Ear, nose and throat disorders and international travel

Abstract

Background

Disorders of the ear, nose and throat may be the most commonly occurring pre-existing health condition in international travellers. Despite their high incidence, there is limited guidance for travellers and their clinicians on their prevention and management. This narrative review addresses this deficit by compiling and discussing available evidence on this neglected subject.

Methods

A comprehensive review of the literature was undertaken using Medine and Scopus databases and multiple combinations of relevant MeSH search terms. Further references were obtained from focused searches on specific issues and manual review of the reference lists of articles obtained from the primary search.

Results

Nasal congestion or discharge are among the most common complaints amongst travellers and various causes are reviewed. Changes in elevation result in a pressure differential between the atmospheric pressure and the middle ear and paranasal sinuses. The effects of air travel, recreational high-altitude exposure and diving are considered. Various causes of epistaxis in travellers such as cold air exposure and recreational cocaine use are discussed. The aetiology of a discharging ear in travellers includes otitis externa. The most frequently described travel-specific aetiology of dizziness is motion sickness while mal de debarquement is a specific subtype which affects travellers and is most commonly associated with sea travel. Surgical tourism for treatment of ear, nose and throat pathology is well established and various precautions are presented for post-operative travel. Obstructive sleep apnoea is discussed from the perspective of international travel. The challenges facing travellers with hearing impairment are explored.

Conclusions

This review critically discusses the prevention, diagnosis, and management of acute and chronic ENT conditions in the travelling population. Several areas of inquiry are highlighted that require further investigation. Close communication between ENT specialists and travel medicine practitioners is recommended in the preparation of selected patients for international travel.

Introduction

Travel medicine is an evolving discipline concerned with the delivery of evidence-based healthcare to travellers who visit foreign destinations [1]. With almost 4% of the world’s population currently living outside their country of origin, migration has reached unprecedented levels [2]. There are many ‘push and pull’ factors driving this, with the perception of more desirable living conditions in some countries, such as Australia and Switzerland, resulting in up to 30% of residents being foreign-born [2]. Although specialised centres exist that provide travel medicine care, a minimum standard is now expected of all healthcare providers who should be aware of the growing health needs of this changing demographic. Almost two thirds of backpackers to Queensland suffered from a medical ailment while travelling yet just over half received pre-travel advice, with a large proportion of those who received it deeming it to be inadequate [3].

Conditions of the ear, nose and throat exert a significant burden on global healthcare, with hearing impairment reported as one of the most prevalent disabilities worldwide [4] and hay fever described as the most common complaint amongst travellers [5]. In spite of this, it remains a neglected aspect of travel medicine which has not previously been reviewed. The purpose of this review is to provide up-to-date information on travel-associated otorhinolaryngological issues and identify any gaps in our understanding of this subject area.

Materials and methods

A comprehensive review of the literature was undertaken using two databases – Medline and Scopus. The databases were searched using the following combinations of MeSH search terms: [Travel* OR Holiday* OR Overseas* OR Abroad OR Touris* Migrant OR Migration OR Foreign] AND [Otorrhea OR Swim* OR Ear OR Otalgia OR Discharge OR Allerg* OR Rhinit* OR Rinorrhea OR Hay* or Allerg* OR Nasal Discharge OR Altitude OR Epistaxis OR Bleed* OR Nosebleed OR Haemorrhage OR Scuba*].

Retrieved articles were manually reviewed with 73 Medline articles considered relevant by title or abstract and extracted for further review. Subsequently, similar search terms were applied to the SCOPUS database with a further 21 relevant articles retrieved. Of all articles screened, only those in the English language were included and any unavailable for online review were omitted. A grey literature search was performed on Google which did not identify any additional literature relevant to the topic of this review. A total of 42 articles were suitable for inclusion. Further references were obtained via targeted searches on specific issues requiring further information as well as manual review of the reference lists of articles yielded by the primary search.

Results

Rhinorrhoea in travellers

Nasal congestion or discharge are among the most common complaints amongst travellers. Anecdotally, there is universal acknowledgement of the negative impact this has on the overall holiday experience. Often this is secondary to an exacerbation of a known, chronic condition whilst in others it is a new issue with numerous potential triggers [6]. Pattern analysis of exacerbations is vital in risk assessment and management of this distressing condition with potential geographical, seasonal and environmental factors being identifiable and potentially preventable.

Allergic rhinitis

Allergic rhinitis, presenting as nasal congestion and rhinorrhoea with variable degrees of associated epiphora (tearing) and sneezing, exerts a significant burden on health care expenditure worldwide [6]. This condition has a varying geographical prevalence, being much more common in North America than China and Mexico, for example [6]. This is multifactorial in nature, with contributions from a combination of nutritional factors, ethnicity, socio-economic status, and adiposity. However, the ‘hygiene hypothesis’ plays a role. It describes the protective nature of early exposure to allergens and infections, which occurs more commonly in rural areas, preventing the immature immune system from adapting towards a pro-allergic state and subsequent development of atopic disorders [6]. Urbanisation of rural areas has been correlated with increased risk, further validating this hypothesis [7].

Sensitisation is a consequence of the adaptive immune response, whereby allergens contact mucosa and, following detection, are presented to the major histocompatibility complex [MHC] by CD4 + T-helper cells, producing allergen-specific IgE [8]. This results in a molecular cascade of events that varies in symptomatology. Atopy is described as an individual’s genetic susceptibility to produce specific immunoglobulins (IgE) on exposure to an allergen [8]. Those not afflicted with atopy are asymptomatic on exposure to the allergen. Prolonged exposure to provocative environmental allergens proportionally reduces the risk of developing atopy, which was shown in a cross-sectional study of almost 100,000 American-born versus foreign-born children in the United States [6]. Children born outside of the US who also had parents born outside of the US had the lowest risk of developing atopy. Conversely, foreign-born US residents who spent a prolonged period in the US were at a higher risk of developing atopic diseases in later life [6]. This phenomenon of ‘residence duration’ has also been demonstrated in many European countries, accounting for a lower disease burden in older migrants given that they had longer exposure to the protective environment [9]. This becomes relevant when risk-assessing patients for travel and when implementing primary prevention strategies in patients who have migrated. Furthermore, individuals who moved house as a child had a statistically significant increase in developing allergic rhinitis, potentially secondary to new indoor and outdoor allergen exposure [6].

With approximately one third of the global population suffering from pollen allergy, or ‘pollinosis’, it poses a sizeable economic burden and negatively impacts on the tourist’s experience [10]. The allergenic hazard of green spaces has been categorised by researchers using a green zone allergenicity index model. Development of these standardised risk index tools involves a complex interplay between ecology, medicine and phenology [10] due to inherent patient characteristics, distribution of endemic flora with varying pollination patterns and allergenic potentials. When implemented, they can aid the at-risk population in minimising environmental exposure during high-aeroallergen seasons. This phenomenon is not unique to the tourism industry, with urban planners incorporating an allergenic index into the selection of trees for city greenspaces, for example [10]. The two most applicable techniques are the risk matrix and the multi-factor model [10]. The latter model has many variants which can be broadly categorised into objective, subjective and combined approaches. The former risk assessment tool is perhaps more standardised and reproducible. Traditionally, a two-dimensional matrix was used as a fundamental risk assessment tool. This allocated a risk score of 1 (low) to 4 (very high) to both the ‘hazard’ of an allergen and the ‘vulnerability’ of the population, plotting them against each other to categorise overall risk. However, this has now been replaced by a three-dimensional matrix model which also incorporates patient resilience factors into the equation. This new matrix is more comprehensive, and the risk can easily be visualised in a diagram (Fig. 1). Table 1 provides a brief overview of some of the common allergens encountered in Europe.

Fig. 1

Assessment matrix of pollen allergy risk (reproduced with permission from Zhou et al., 2022) [10]

Table 1 Most prevalent allergens in the Mediterranean and wider European regions

Climate change has significantly impacted tourist behaviour as well as accelerating the onset, prolonging the duration and increasing the intensity of the pollen season with rising CO₂ levels predicted to increase the likelihood of seasonal allergies in the United States by 200% by the end of this century [10]. Increasing temperature, precipitation and wind speed changes are also factors of climate change and urbanisation, all of which impact pollen count and will help dynamic risk assessment in the coming years [10, 15]. The associated increases in humidity promote the growth of house dust mites and mould which further contribute to allergic rhinitis [15]. Ragweed (Ambrosia artemisiifolia), a common aeroallergen, is predicted to have sensitised much of the European population by 2060 (Fig. 2) [16]. It may be concluded that environmental factors will have a much more significant impact on human health over the coming decades, although the exact extent of this remains unclear.

Fig. 2

Proportion of population sensitised to ragweed with baseline (current) levels on the left and predicted (future) levels on the right (reproduced with permission from Lake et al., 2017) [16]

Air pollutants and temperature

Poor air quality negatively impacts both the upper and lower respiratory tract [15]. Massive economic and industrial growth increases in the last century have led to declining air quality and dramatic increases in airway diseases worldwide, such as nasal irritation and asthma [17]. The Centers for Disease Control and Prevention (CDC) provide comprehensive information on air pollutants, with ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO), lead (Pb), sulphur dioxide (SO₂) and fine particulate matter (PM_2.5) being the main contributors [18]. Ozone itself is multifaceted, with high levels in the stratosphere filtering out harmful ultraviolet radiation whilst large amounts at ground level are harmful [19]. Exposure of the nasal mucosa to these irritants is pro-inflammatory with resultant rhinitic symptoms [20]. Prolonged ambient exposure is thought to lead to mucosal remodelling and chronic inflammation; however, it is difficult to disentangle these data from confounding factors [20]. The primary source of ozone is industrial and from traffic; however, with rising temperatures a secondary source becomes important. Increased nitrogen dioxide and other volatile precursors are converted to ozone on exposure to sunlight [19]. This leads to the development of what is colloquially termed ‘summer smog’, the presence of which exacerbates these health issues [19]. The CDC regularly update their website (https://www.cdc.gov/environmental-health-tracking/php/data-research/air-quality-outdoor.html?CDC_AAref_Val=https://www.cdc.gov/nceh/tracking/topics/airquality.htm) in an effort to provide accurate information on both long-term trends and short-term spikes of this smog, with urbanised areas having higher prevalence, which may influence travel or migration habits [18]. Destinations where legislation does not prohibit indoor smoking also have a strong association with nasal irritation and the potential to aggravate symptoms in susceptible individuals [21]. For many, travel to these regions is the main source of exposure to environmental tobacco smoke and those naive to the exposure have a much higher risk of nasal symptoms when exposed on holiday (58% v 36%) [22]. Researching local smoking legislation habits before travel will help the tourist plan accordingly.

Exposure to changes in temperature, most commonly cold air, can induce vasomotor rhinitis due to nasal mast cell activation and sensory nerve stimulation [23]. This manifests as rhinorrhoea, nasal congestion and a burning sensation. This condition is easily reproducible; nasal cold, dry air provocation tests induce symptoms within minutes which dissipate soon after test termination [23, 24]. Individuals have varying levels of nasal hyperresponsiveness and it is suggested that those with heightened nasal cold air sensitivity have a reduced ability to compensate for the water loss associated with exposure to cold environments [23]. On this basis, the symptoms of cold air-induced rhinitis may reflect the activation of compensatory cholinergic mechanisms in an attempt to restore mucosal homeostasis [23]. Therefore, anticholinergic agents are effective in alleviating symptoms in affected individuals [23].

Infective rhinitis

Travel is frequently associated with the spread of infections. Transmission from travellers to host populations is uncommon, with the greatest risk being to the traveller on exposure to new pathogens [1]. Contributory factors include, but are not exclusive to, disease prevalence in a region along with intrinsic patient factors, such as general health and vaccination status [1]. In respiratory tract infections, the nasal and oral mucosa are the most common sites of initial contact with exposure eliciting a cascade of events which may result in disease development [25]. Given the airborne and droplet nature of spread associated with these respiratory pathogens, a reduction in transmission rates is inversely proportional to mask-wearing implemented during the COVID-19 pandemic [26]. Traditional teaching recognises an increased frequency and duration of indoor congregating during winter, promoting person-to-person transmission, with a notable increase in viral illnesses during winter months [25]. Although this is likely a contributing factor, recent studies also show that cold environments blunt nasal immunity which increases susceptibility to development of an infection on exposure to a pathogen [25]. As part of the innate immune system, the nasal epithelium produces extracellular vesicles which suppress viral antigen particles.²⁵ Total production of these vesicles is diminished in cold environments, increasing risk of viral symptoms post-exposure [25].

Mucociliary and phagocytic function are also impaired at high altitudes and cold environments, further increasing risk to the traveller [27]. The hypobaric and hypoxic environments associated with elevated altitude contribute to a complex interplay of adaptive metabolic disturbances [28]. It has been reported that both neutrophil and lymphocyte number and function are significantly reduced after a mere few hours of exposure to high altitudes [28]. Short-term exposure may induce chronic changes owing to the production of cytokines and antibodies [28]. T-cell mediated immunity may also be blunted in hypobaric environments [28]. Altitudes of greater than 4000 m induce pro-inflammatory states via excessive production of circulating Interleukin-1, Interleukin-6 and C-reactive protein amongst others [28].

Travel facilitates the transmission of influenza viruses, especially in the setting of mass gatherings, air and cruise ship travel, with the greatest risk occurring in the extremes of age and in the immunocompromised traveller and in travellers with chronic cardiorespiratory illnesses. Pre-travel advice and preventative measures, including seasonal influenza vaccination, are discussed in detail in authoritative reviews published in the travel medicine literature [29, 30].

Barometric pressure changes

High altitude exposure

Changes in elevation result in differentials in pressure between the external atmospheric pressure and pneumatised areas of the body, most notably the middle ear and paranasal sinuses [31]. Ascent causes a decrease in atmospheric pressure with resultant expansion of air within the middle ear [31], with the opposite effect occurring on descent. The pressure normally equalises via air escaping down the Eustachian tube into the nasopharynx [31]. Anything which interferes with this mechanism, such as rhinitis or anatomical variants as well as iatrogenic factors, predisposes to barotrauma and otalgia which is most common during descent [31, 32]. Up to 20% of commercial air passengers experience an element of barotitis (middle ear injury secondary to pressure changes), with most self-resolving [33]. Some studies quote up to 83% of travellers being affected [34]. Given that almost two million people take commercial flights annually, this leads to a large number of affected individuals [35]. Pharmacological and non-pharmacological preventative approaches can be employed, yet a third of travellers are unaware of these, highlighting the need to provide education on the topic [34]. Administration of a decongestant, such as oral or topical pseudoephedrine, 30 min before a flight, reduces the risk [33, 35, 36]. In the paediatric population, however, where flight-induced otalgia affects up to 15%, there has been no proven benefit to the use of a nasal decongestant [32, 37]. The most commonly described non-pharmacological measure is to induce swallowing in an effort to decompress the Eustachian tube [32]. Various techniques have been described ranging from bottle-feeding in infants to Valsalva techniques and gum-chewing in older individuals [32].

Rapid changes in pressure result in mucosal oedema which causes transient narrowing of the nasal airways and nasal congestion, but subsequent narrowing of the sinus ostia can also cause sinus pain during changes in environmental pressure, known as barosinusitis [38, 39]. Underlying sinus infections or rhinitis increase the risk and severity [39]. Mucociliary transport time is altered at high altitude which can disrupt nasal physiology [40]. This may lead to the development of nasal congestion and impaired clearance of secretions. Administration of saline drops is a simple yet effective way of reversing some of these changes or as a primary prophylactic measure [40]. Nasal congestion and higher oxygen demand at elevated altitudes necessitates obligatory mouth breathing. This bypasses the natural humidification and warming of inhaled air which is thought to irritate the pharynx and induce an element of pharyngitis, with potential cough, in most individuals [41]. The ears and nasal tip are particularly prone to cold-induced injuries such as frostbite and its resultant tissue loss [41]. Education on protective measures (minimising exposure and use of appropriate cover) are important in those at risk.

Diving and barotrauma

The physiological effects of exposure to hyperbaric underwater environments are often underestimated [42]. Approximately 80% of divers experience an ear, nose and throat-related complaint at some point in their diving career [38]. Pressure rapidly increases with small changes in water depth, with the pressure gradient at the surface to 10 m in depth equivalent to the difference between sea level and outer space [42]. In practical terms, gas volume doubles in size when an individual 10 m below sea level rises to the surface, which poses obvious problems in closed air-filled cavities like the middle ear. Barotrauma is a result of the imbalance between pressure in the middle ear and surrounding pressure outside the body [43]. The Teed classification can be used to categorise otic barotrauma on the basis of tympanic membrane appearance from 0 (normal) to 5 (perforation) [38].

Similar to high altitude, descent during diving is more likely to elicit symptoms than upon ascent [34]. Likewise, various equalising techniques can be undertaken to minimise barotrauma and appropriately trained diving instructors will ensure correct technique. Longer surface duration between dives has been proven to reduce the risk [43]. A feet-first approach with equalisation of ears three times per metre up to five metres is also preventative [38]. Inexperienced divers have higher middle ear peak pressures, pressure changes on Valsalva manoeuvre and elevated risk of barotrauma with regular divers having an overall more negative middle ear pressure [44]. Topical and oral decongestants play a preventative role [42]. Without equalisation, tympanic membrane perforations can occur at depths as shallow as 2 m [44] and at further depth there is a risk of significant barotrauma which can affect the outer, middle or inner ear with some documented cases of perilymphatic fistulae and facial nerve palsies if the bony canal is dehiscent, as well as hearing loss [42]. Therefore, should a diver have difficulty equalising they should ascend and attempt an alternative technique, such as the Frenzel manoeuvre (tongue to roof of mouth while pinching nose) or Toynbee Manoeuvre (pinching nose and swallowing) [38]. If these also fail, the dive should be aborted. Given that equalisation techniques are ineffective in patients with tympanic membrane perforations or patent tympanostomy tubes, diving is contra-indicated in these cases [42].

Similar to air travel, gas expansion and compression on ascent or descent can cause significant sinus pain. In extreme cases, facial bone fractures can occur with associated surgical emphysema and pneumocephalus [38]. Primary prevention with topical or oral decongestants can reduce risk, with functional endoscopic sinus surgery indicated in severe, recurrent cases [38].

It is not uncommon for sea anemone or coral exposure to occur while diving. Several species produce toxins which induce angioedema on exposure [45]. These potentially life-threatening sequelae should be recognised and medical advice sought in suspected cases. Swimmers and divers should be aware of the subtype of sea anemone endemic to an area of sea water activities to minimise risks of exposure. Rarely, laryngospasm can occur at depth with catastrophic consequences. This is fortunately very uncommon with only rare reports in the literature [38].

Altitude and the ears

Repeated compression and decompression experienced by the middle ear is believed to negatively impact hearing [43]. A conductive element is usually secondary to tympanic membrane injury or middle ear effusions but may also occur as a result of bony canal exostoses [44]. These are localised bone growths secondary to the repetitive trauma and cold-water exposure and are benign in nature [38], predisposing to retained moisture and recurrent otitis externa [38]. Divers are also thought to be at risk of sensorineural hearing loss. Inner ear barotrauma is a spectrum of pressure-related pathologies from degeneration of the organ of Corti, perilymphatic fistulae formation, intra-labyrinthine membrane tears, and production of noxious stimuli as a result of the trauma [44]. Audiograms typically show a dip at 4–8 kHz but most studies fail to demonstrate statistical significance [43]. Bed rest with head elevation helps to replenish perilymph leak, restore ionic gradients and ultimately resolve the majority of these hearing issues [43]. Although symptoms may diminish as these adaptations occur, it is advised to undergo formal vestibular testing given the risk for symptom progression [43].

One hypothesis for development of sudden sensorineural hearing loss is cochlear ischaemia. During commercial flights, cabin pressurisation drops the PaO₂ from 95mmHg to 60mmHg resulting in a 3–4% drop in circulating oxyhaemoglobin [35]. However, it has been shown that these pressure changes associated with air travel have no detrimental effect on those with known idiopathic sudden sensorineural hearing loss [35].

The haemodynamic changes associated with altitude typically come into effect above 3,500 m [27] and can cause significant oedema of neuronal tissue and subsequent vestibulocochlear nerve dysfunction manifesting as hearing loss and vertigo with severe symptoms developing at approximately 6,000 m [46]. Auditory localisation is also impaired at altitude which can result in further disorientation and inability to interpret hazardous circumstances [46]. In addition to this, cochlear function diminishes at core body temperatures of 30 degrees and under [27]. Once acclimatised to new altitudes, patients usually return to baseline [46] so high-altitude trekkers should be counselled about this phenomenon and can be conservatively managed with bed rest and potential vasodilator use. Symptoms usually resolve within three days [46].

Vertigo, which is discussed in a later section of this review, can also complicate recreational dives. Lack of proprioceptive input, visual cues and the feeling of weightlessness all increase reliance on an intact vestibular system [43]. A unilateral temperature or pressure input difference to one ear will stimulate the vestibular system by changing the density and temperature of the endolymph contained within the semicircular canals [43]. In cases of tympanic membrane perforations, this discrepancy between ears is larger and the cold caloric stimulus results in transient dizziness [38, 43]. Furthermore, if a discrepancy exists between right and left-sided Eustachian tube function, a patient may experience a phenomenon known as alternobaric vertigo, where the pressure difference between the two ears triggers a vertiginous episode [38]. Associated underwater vomiting with any of these can be fatal. Cerumen (wax) impaction can hinder equalisation and expand during dives, manifesting as otalgia [38]. Otomicroscopy with wax removal pre-dive can address this health issue. Tinnitus is a well-documented symptom experienced with altitude and pressure changes and is usually intertwined with one of the above aetiologies. Whilst most causes are not fully understood, they tend to spontaneously resolve by 6–12 months as the damaged sensory endings within the cochlea either regenerate or undergo apoptosis [43].

Epistaxis

The nasal mucosa is a highly vascular structure with a rich blood supply from various named vessels including the sphenopalatine artery, anterior ethmoidal artery, posterior ethmoidal artery, superior labial artery and greater palatine artery [47]. Epistaxis results when one of the blood vessels ruptures and occurs anteriorly in Kiesselbach’s plexus (Little’s area) in 90% of cases [47]. It is a common complaint, with up to 60% of the population experiencing it during their lifetime, 6% of whom require medical intervention [48]. Epistaxis has many potential aetiologies that can be broadly categorised into local, systemic or environmental in nature. Inflammation of the nasal mucosa, secondary to any of the above aetiologies, poses an increased risk of bleeding from superficial mucosal vessels [47]. Preventative measures can be taken to minimise the risk. Drying out of nasal mucosa in cold environments increases the risk of epistaxis [27]. The use of barrier protection, using over the counter petroleum jelly or various non-medicated products, has proved effective in both primary prevention and recurrent episodes [48]. In instances where nosebleeds do occur, avoiding strenuous activities, digital manipulation and nose-blowing minimise recurrence risk [47]. Vasodilatory effects of hot environments, including hot showers or intake of hot beverages with steam, also increase re-bleeds and thus should be avoided for a number of days after an episode of epistaxis [47]. Alcohol consumption, which generally increases in holidaymakers, leads to both precipitation and prolongation of bleeding episodes due to a number of factors including vasodilatory effects, inhibition of platelet aggregation, and promotion of changes in blood pressure [49]. Recreational use of intra-nasal cocaine also increases during holiday seasons and in tourist areas [50]. The mucosal irritation and local vascular effects increase the risk of epistaxis [50]. Physical altercations as a result of intoxication proportionally rise as do cases of trauma-induced facial injuries which are associated with nasal trauma and epistaxis [51]. When diving, mucosal irritation and gas expansion on ascent may cause up to 3% of divers to experience recurrent epistaxis [38]. This is usually self-limiting and slow ascent may help to prevent it [38].

The discharging ear

Otitis externa is a common condition in which the lining of the external auditory canal becomes inflamed, painful and discharges [43], with the majority of cases being infective in origin. Swimmers and divers are five times more likely to suffer from otitis externa than the general population and should be counselled on its high prevalence and consider prophylaxis [42.43]. Retained moisture and introduction of new microbes, predominantly Pseudomonas aeruginosa and Staphylococcus aureus, along with breakdown of the naturally acidic protective element of cerumen, predisposes swimmers and divers to otitis externa [38, 43, 44]. The flora of regular swimmers often shifts from a gram-positive to a gram-negative predominance [52]. Head submersion is the biggest risk factor, with level of water contamination and duration of exposure not being statistically significant [52]. Therefore, all travellers should be counselled on this risk even if only brief submersion is expected in apparently clean water. Warmer environments may induce sweating as well as increased humidity, both of which increase the moisture content of the ear canal, further predisposing travellers to otitis externa. A higher prevalence of Pseudomonas aeruginosa occurs in summer months [53] which has clinical relevance when treating the disease.

Water precautions can be used as a form of prevention and can be implemented in several ways including use of ear plugs or cotton wool (mechanical); topical antimicrobial agents peri-exposure (chemical); and avoiding head submersion in water (behavioural). The inconvenience and associated anxiety of water restrictions often negatively impact a holiday and may not be followed by all tourists [54]. Use of acidic drops can help restore the pH balance and inhibit growth of the pathogenic organisms [38]. In cases of tympanic membrane perforations, exposure to hypertonic water in sea swimming affects the mucociliary physiology of the middle ear mucosa, increasing the risk of chronic otitis media [44]. Pseudomonas aeruginosa is a common pathogen [42] with chlorinated water having fewer organisms identified than untreated water [55] and outdoor pools having a statistically significantly lower bacterial load than indoor pools. Up to 30% of European strains demonstrate antimicrobial resistance to at least one antibiotic [55]. With a third of pools analysed in a Spanish study failing to meet expected disinfection standards [55], travellers need to be aware of the risk of potential exposure in these common tourist destinations and potentially more in less developed areas [55].

In patients susceptible to ear infections or those with operated-on ears, access to local health services may be essential and disparities in healthcare should be anticipated. In many less-developed countries, lack of local resources results in a delay in receiving timely and effective treatment [56]. Local healthcare options should be explored before travelling to such regions, especially by susceptible individuals with pre-existing conditions.

Occasionally, otorrhoea and otalgia can be caused by live foreign bodies. Whilst this can occur anywhere, patients who sunbathe in warm countries are theoretically at higher risk [57]. If visualised on otoscopy, the insect must be killed by administration of 1% lignocaine or an alternative in case bites or trauma result from attempted removal and potential venom is released into the patient [57]. Rarely, flies can lay eggs in the ear canal with potentially catastrophic consequences [58]. Cochliomyia hominivorax is an example of a fly that caused devastation of animal livestock before eradication by release of sterile male flies in southern US states in the 1960s [58]. They are still a health concern in some less developed countries, with case reports of larvae causing significant local tissue destruction [58]. Therefore, it is vital that physicians are aware of this phenomenon when treating returning travellers for painful otorrhoea to ensure prompt diagnosis and management with surgical debridement and antimicrobial agents.

The dizzy traveller

Dizziness remains one of the most common emergency presentations worldwide with the differential broadly categorised into central and peripheral causes [59]. The most frequently described travel-specific aetiology is motion sickness which most of the population experience at some stage in their lives. The pathophysiology is believed to relate to the brain’s receipt of conflicting sensory input from the eyes, peripheral vestibular apparatus and organs of proprioception during exposure to passive movement while travelling [59]. Symptoms vary but include dizziness, malaise, nausea, vomiting, disorientation, and headache [59]. A combination of behavioural and pharmacological measures are beneficial [59]. Avoidance and habituation of triggering environments can minimise symptoms in those affected. Pharmacological agents with vestibular-sedating effects, such as anticholinergics and antihistamines, play both a preventative and abortive role.

Closely related to this is the condition commonly referred to as ‘land sickness’, or post-motion vertigo. Aforementioned symptoms generally persist, or have their onset, on disembarking a ship but rarely persist beyond 48 h and, similar to motion sickness, are responsive to vestibular therapy [60]. Mal de debarquement syndrome (or ‘sickness of disembarkment’) is a benign yet debilitating neurological condition characterised by the prolonged self-perception of rocking, bobbing, or swaying following a period of prolonged passive motion [60]. Some patients also experience associated cognitive dysfunction, anxiety-depression and headaches with some describing heightened sensory sensitivity. Despite being first described in 1987, the underlying aetiology of this disorder remains poorly understood [58]. It is thought to be secondary to the body’s vestibular system becoming habituated to the rocking and rhythmic movement of travel with associated neuroplasticity resulting in sensory rearrangement. It is most commonly associated with sea travel but has been described in both air and terrestrial travel [59]. It is a diagnosis of exclusion with investigations for central causes taking priority. Neurological examination is typically normal and in the presence of objective findings an alternative diagnosis should be sought. Limited literature on the topic highlights the lack of physician awareness of this phenomenon and the resultant diagnostic delay [61].

Guidelines have been developed to aid diagnosis which can be grossly summarised as unwavering symptoms of self-perception of motion lasting longer than one month, present when stationary and resolved by motion with normal clinical examination, imaging and laboratory work [61]. Unlike peripheral causes, patients typically have no improvement on exposure to vestibular sedatives and symptoms classically last longer than a month, with some studies describing debilitating symptoms persisting for years [60]. Whilst being resistant to readaptation to stable environments, most patients experience resolution of symptoms on re-exposure to the incident motion. Selective serotonin reuptake inhibitors (SSRIs) and psychotherapy are beneficial with short-acting benzodiazepines also having a role in symptomatic relief. Pharmacological migraine therapy, such as topiramate and verapamil, has also been described [61]. Most cases resolve spontaneously without intervention [60].

ENT surgery and international travel

Surgical tourism is a rapidly evolving area of healthcare. The tendency, and sometimes necessity, to travel for surgery is becoming increasingly more common [31], often resulting in premature post-operative air travel. Along with the issues discussed earlier in relation to altitude, this creates other potential problems.

Post-operative considerations in travellers

Middle ear surgery

Given the effects of altitude on the middle ear, most specialists would advise against air travel for at least two weeks following middle ear surgery [32]. However, it is worth discussing this with the operating surgeon. Iatrogenic tegmen defects of the skull base have the potential to allow translocation of middle ear flora due to the air expansion with resultant meningitis [31].

Grommet insertion

Tympanostomy tubes play a protective role in reducing barotitis and otalgia and are not in themselves a contraindication to air travel [32]. A consensus on the requirement for water precautions post-grommet insertion has always been difficult to achieve given the variables involved, including bacterial load of the water, duration of exposure, and patient factors [62]. Whilst there is a theoretical risk of water penetration and translocation of skin flora (i.e. Staphylococcus aureus and Pseudomonas aeruginosa) through the grommet, the culprit pathogens causing most grommet infections are commensals of the nasopharynx (Haemophilus influenzae and Streptococcus pneumoniae) [62] suggesting migration of bacteria up the Eustachian tube as a pathogenetic mechanism. Water precautions can be implemented in a number of ways as described earlier. The inconvenience and associated anxiety of restrictions on water-based recreational activity negatively impact holiday experiences and are only shown to reduce infection risk in the first month post-procedure [54]. Despite clinicians being slow to adapt to them, current guidelines no longer recommend water precautions in these patients [60]. Diving is contra-indicated in these travellers, however [42].

Tracheostomy

Whilst there are no contraindications to air travel with tracheostomies or laryngectomies, altitude increase and pressure changes dry out the respiratory mucosa and increased frequency of nebulisation is essential [41]. Submersion of a laryngectomy stoma or tracheostomy under water poses an immediate threat to life due to aspiration. Therefore, affected individuals should be educated about this issue. Various devices have been designed to tackle this problem and permit water-based activities in this patient cohort (Fig. 3) [63]. Table 2 summarises clinical recommendations for air travellers who have recently undergone ENT procedures.

Fig. 3

Schematic depicting stoma occlusion device (reproduced with permission from Denning et al., 2021) [61]

Table 2 Compilation of useful web-based resources for travellers and their healthcare providers

Obstructive sleep apnoea and travel

Sleep disordered breathing is a medical condition that has strong associations with obesity. Therefore, the substantial increase in obesity in developed countries in recent years is reflected in the growing prevalence of sleep disordered breathing, with an estimated 20–30% males and 10–15% females affected [64, 65]. Obstructive sleep apnoea (OSA) falls under this diagnosis and many patients are managed with non-invasive ventilatory devices such as continuous positive airway pressure (CPAP) devices [66]. Up to half of airlines permit their use during air travel but the majority require a medical statement in relation to this. These airlines outline specific requirements and permit particular models only [66]. Most airlines and cruise ships place the onus on patients to ensure their device is compatible in advance of travel, with the traveller expected to ensure adequate battery life and a compatible power source [65]. Therefore, it is vital that travellers incorporate this into their travel plans, especially given that obstructive symptoms can be exacerbated by the cabin pressure altitudes of commercial aircraft. Modern CPAP machines operate around the world and can be used safely without a voltage converter in most countries. An international plug adaptor may be required to ensure that the device’s power cord is compatible with the power sockets (outlets) of the destination country.

Hearing impairment and travel

Travelling can be a daunting experience for some but facing it with an underlying disability adds an extra layer of complexity. Deaf travellers face unique risks not experienced by unaffected individuals and these are often overlooked [67]. Even mild, age-related hearing loss negatively affects the holiday experience and, due to an ageing population, is becoming more prevalent with one in three older adults affected [67]. Foreign-accented speech typically requires more processing effort which is accentuated in noisy environments [67], making older adults struggle in social situations while abroad. Exposure to multiple foreign accents has been shown to have a short-term benefit in adapting to speech [68], suggesting value in providing travellers with audio sources to listen to pre-travel.

Patients with implanted hearing amplification devices, such as bone-anchored hearing aids and cochlear implants, should carry an official medical letter or information sheet on the device for airport security [69]. Furthermore, these devices usually have an international warranty but prior to travel these factors should be explored and discussed [69]. External processors should be removed prior to water-based activities but implants are safe for participation [69]. Patients should be aware that, without the external processor, their hearing will be affected, and this may put them at risk of identifying potentially dangerous surroundings.

Food allergies and travel

Food allergens remain a global concern and, while the prevalence of allergies varies from region to region, so do food labelling requirements [70]. Even with heightened consumer awareness, many consumers are unable to interpret food labels correctly and this is more of a concern with foreign languages [70]. Lack of universal labelling laws in addition to the variability of language displayed are a global health concern and, until these are internationally standardised, travellers should research destinations and local laws carefully. It is also worth noting that many travellers will encounter novel foods they may not have consumed before and therefore have an unknown allergic status. Travellers should be aware of early signs of anaphylaxis, such as lip and tongue swelling, and they and their travelling companions should know how to seek emergency medical attention. This is particularly critical for air passengers, their travelling companions, and commercial flight crew members. Readers are referred to a recent comprehensive review of in-flight allergic emergencies for in-depth coverage of this topic [71].

Dysphonia

Voice production can be impaired by several travel-related factors. These include voice overuse, alcohol and caffeine ingestion, dehydration, and smoke inhalation. Therefore, travellers are usually at higher risk of losing their voice [72]. Practicing good vocal hygiene by minimising exposure to triggers and maintaining hydration will improve the overall holiday experience [72].

Skin cancers of the head and neck

Cutaneous malignancies are a growing problem. Sun exposure, along with high altitude, are important risk factors in travellers [73]. The head and neck is considered a high-risk area for cutaneous squamous cell carcinoma, with earlier local invasion and risk of distal spread, so travellers should exercise caution by minimising sun exposure and undertaking protective measures [74]. Table 3 provides a compilation of useful online resources which may be consulted by travellers and their travel health advisors.

Table 3 Guidance on commercial air travel in specific ENT conditions*

Discussion

Strengths of review

This review synthesises the most current, evidence-based information on the influence of travel on individuals with a wide variety of conditions of the ear, nose and throat and the impact of these disorders on international travel. While the focus of our review is on conditions which are actively managed by otorhinolaryngologists, it also addresses other pertinent topics typically investigated by non-ENT specialists such as allergic disorder, obstructive sleep apnoea and the traveller with loss of balance. The travel-related advice to patients who have undergone operative ENT procedures will be of particular value to travel medicine practitioners who are faced with queries about fitness to travel as air passengers in particular.

Limitations of review

While this review is the first to focus on the topic of travel-associated issues affecting the ear, nose and throat, it is subject to limitations. Our search strategy was limited to articles indexed in two databases and published in the English language. Due to the international nature of this topic, reliance on one language may have led to selection bias with potential omission of literature published in other languages. Furthermore, this is an under-researched area so a large proportion of articles reviewed were from targeted searches performed by the primary author, perhaps resulting in relevant articles being overlooked.

Potential avenues for future research

It would be of interest to investigate the prevalence of otic barotrauma, sinus pain, and ear discomfort in air passengers and to evaluate the quality of preventive travel health advice available on public websites, including that provided by commercial airlines. We are also not aware of any research on the use of ear plugs or noise-cancelling devices in air passengers. There have been no studies to date on the strategies employed by long-term travellers or expatriates for the management of chronic rhinosinusitis. It would be potentially valuable to examine how jet lag influences symptoms of sleep apnoea in affected travellers. Finally, it would be of great interest to investigate the effectiveness of respiratory vaccines, including influenza vaccine, in the prevention of ENT-related infections during travel.

Conclusion

This comprehensive narrative review of the literature characterises conditions affecting the ear, nose and throat in international travellers whilst highlighting the overall lack of dedicated research on the topic. The review aimed to increase awareness in an effort to optimise prevention, diagnosis and management of both acute and chronic ENT conditions in the travelling population. There are several areas that require further investigation and this article may stimulate further original research. We recommend close cooperation between ENT specialists and travel medicine practitioners in preparing patients for international travel.