Introduction
The external auditory canal has two parts: cartilage and bone. The cartilaginous part forms the outer part of the canal and comprises 40 per cent of it. Bony parts form the inner part of the canal and comprise 60 per cent of it.Reference White, Ananthakrishnan, McKean, Brunton, Hussain and Sudarshan1 Subcutaneous tissue is thin in the cartilaginous part. In the bony part, soft tissue is rather firm between the periosteum, skin and bone. The skin of the external acoustic meatus consists of keratinised, stratified squamous epithelium.Reference White, Ananthakrishnan, McKean, Brunton, Hussain and Sudarshan1 It includes hair follicles, and sebaceous and apocrine glands. Secretions of these glands, in combination with squamous epithelium, form the acidic part of the cerumen and have protective features. Hair follicles and secretions of the sebaceous and apocrine glands are the main protective mechanisms in the external acoustic meatus.Reference Stroman, Roland, Dohar and Burt2, Reference Pabla, Jindal and Latif3 The external acoustic meatus has a self-cleaning structure which protects against infections. However, external manipulations to the external acoustic meatus (e.g. frequent cleaning, which involves the insertion of foreign bodies, and the use of local steroids for therapeutic purposes) disrupt this protective mechanism and cause predisposition to infection.Reference Stroman, Roland, Dohar and Burt2, Reference Pabla, Jindal and Latif3
The aetiology of an itchy ear canal has not been fully identified. It is suggested that the most common cause is allergic contact dermatitis.Reference Li and Cruz4 Excessive manipulation using ear cleaning apparatus can cause a reduction or interruption in cerumen and apocrine gland secretion. This decline leads to a vicious cycle of dryness and persistent contact dermatitis in the external acoustic meatus.Reference King5
An itchy ear canal, which is a frequent symptom encountered by ENT clinicians, is usually seen in adults. The most common complaints are itching, pricking sensation and pain in the external acoustic meatus. The severity of itching varies from individual to another; some individuals complain of severe itching that can cause wakening from sleep, while others complain of mild itching. There is often no definitive reason for the skin diseases or infection that can be detected by otoscopic and microscopic evaluations, and the aetiology remains unclear in affected patients.Reference King5
Demodex is a species of mite that is commonly present in the facial region of humans. It has been suggested that Demodex folliculorum and Demodex brevis mites can be transmitted by close contact in human hosts.Reference Aycan, Otlu, Karaman, Daldal and Atambay6 These mites, which are mainly localised in the hair follicles and sebaceous glands of the face, are also found in the forehead, cheeks, nose and nasolabial regions.Reference Aycan, Otlu, Karaman, Daldal and Atambay6 It has been reported that D folliculorum has a role in the aetiopathogenesis of rosacea, blepharitis, folliculitis, acne vulgaris, papulopustular lesions of the scalp and pustular lesions of patients with acquired immune deficiency.Reference Baima and Sticherling7, Reference Magro and Crowson8 The diagnosis of demodex species infestation is made by parasitological evaluation of skin samples obtained by an adhesive band, skin scraping, punch biopsy or standard superficial skin biopsy.Reference Aycan, Otlu, Karaman, Daldal and Atambay6 In the present study, we aimed to investigate the frequency of demodex species in the external acoustic meatus of patients without a skin disorder or infection, who presented to the ENT out-patient clinic with an itchy ear canal.
Materials and methods
A total of 155 patients aged 18 years or older, who were seen at the ENT out-patient clinic of Mustafa Kemal University School of Medicine, were prospectively included in the study. Those with dermatological disease, infection, otomycosis, chronic and/or acute otitis media, a dermatological disorder on the skin of the external acoustic meatus, a mass on the external acoustic meatus, or a congenital anomaly were excluded from the study.
Before taking samples, the ear canal skin was cleaned of cosmetic materials. Patients were assigned to one of three groups as follows: group one comprised patients who had used 1 per cent dexamethasone sodium phosphate over 10 days within the last 3 months for an itchy ear canal; group two consisted of those with an itchy ear canal who had not received any drug treatment in the last 3 months; and group three was composed of healthy individuals who acted as controls. Skin and hair samples were collected from one ear, from the medial region of the tragus of the external acoustic meatus, using a curette. The samples were placed in sterile tubes containing glycerine and immediately transferred to the laboratory. All samples were promptly evaluated for parasites using light microscopy (Figure 1).
Light microscopic image of the parasite. (Original magnification 40×)
Statistical analyses were performed using SPSS® software, version 15.0. Categorical variables were expressed as number and frequency, whereas continuous variables (years) were expressed as mean ± standard deviation. A normal distribution of continuous variables (years) was tested using the Kolmogorov–Smirnov test. For comparisons among groups, the chi-square test or Fisher's exact test was used to compare categorical variables, whereas the Mann–Whitney U test and Kruskal–Wallis test were used for the comparison of continuous variables. A p value of less than 0.05 was considered to be statistically significant in all tests.
Results
A total of 155 patients were included in the study; 54 (34.8 per cent) were in group one (local steroid group); 51 (32.9 per cent) were in group two (no local agent group), and 50 (32.3 per cent) were in group three (control group). Mean ages were 39.98 ± 15.55 years in group one, 37.70 ± 13.07 years in group two and 37.52 ± 15.48 years in group three. Mean age was similar among the three groups. Of the subjects, 61.3 per cent (n = 95) were men and 38.7 per cent (n = 60) were women (p = 0.005).
Demodex species was positive in nine (5.8 per cent) of the patients. Six of these positive cases were in group one, two in group two and one in group three. The frequency of demodex species in the external acoustic meatus was significantly higher in patients using a local steroid (group one) compared with those not using a local agent (groups two and three) (p = 0.046; Figure 2), but was similar between those patients with an itchy ear canal who did not use a local agent (group two) and healthy individuals (group three) (p = 0.571).
Distribution of the parasite in the three groups.
Of the nine cases with demodex species positivity, 66.7 per cent (n = 6) were women and 33.3 per cent (n = 3) were men (p = 0.077). Mean age in demodex species positive cases was 54.44 ± 12.66 years, whereas it was 37.45 ± 14.28 years in the demodex species negative cases (p = 0.001).
Discussion
To the best of our knowledge, this is the first study in the literature in which the frequency of demodex species was investigated in ear skin scrapes of patients with an itchy ear canal.
Cerumen protects the external acoustic meatus against physical factors and invasion by micro-organisms. Beta-defensin-1 and beta-defensin-2, lysozyme, lactoferrin, and secretory immunoglobulin A also have an important role in the protection of the external acoustic meatus. However, these protective mechanisms can be disrupted by external manipulations such as ear cleaners and local steroids used for therapeutic purposes, and this causes predisposition to infection.
In our study, parasite frequency was significantly higher in patients using local steroids. However, as the proportion of patients with demodex-positive samples was very small in this study, the significant p value may be a false positive. Therefore, further studies with a larger patient series are required to confirm our findings. The aetiology of an itchy ear canal has not been fully elucidated, although predisposing factors are well known.Reference Stroman, Roland, Dohar and Burt2, Reference Roland and Marple9
In several studies, demodex species have been found to be more frequent in patients with acne rosacea when compared with the normal population. This rate was further elevated in those using topical steroids.Reference Li and Cruz4–Reference Baima and Sticherling7, Reference Liu, Sheha and Tseng10 In our study, as mentioned previously, demodex species were more common in patients with an itchy ear canal who were receiving local steroids.
It has been reported that D folliculorum and D brevis are usually localised in hair follicles and sebaceous glands in the pilosebaceous units of the face. They live singly or in groups at follicular openings.Reference Aycan, Otlu, Karaman, Daldal and Atambay6 The mites are often localised at the base of the cilia, chin, forehead, and, rarely, in the external acoustic meatus, nipple, penis and hip.Reference Dong and Duncan11 There are only a limited number of studies on the frequency of these mites in the external acoustic meatus, which has hair cells, and sebaceous and apocrine glands. In one study, the frequency of demodex species in secretions of the external acoustic meatus was reported to be 11.58 per cent and the majority of patients complained of an itchy ear canal.Reference Ding and Huang12 In our study, the rate of demodex species positivity was found to be 7.6 per cent in patients with an itchy ear canal (groups one and two; n = 105), whereas it was 5.8 per cent among all patients (groups one, two and three; n = 155).
Although it is thought that the demodex species, the most commonly seen ectoparasite in humans, is the aetiological agent in many skin disorders, its detection in healthy individuals raises a discussion about the pathogenic role of these mites in disease.Reference Pena and Andrade Filho13 In the present study, no significant difference was found in the frequency of these mites in patients with an itchy ear canal who did not use topical steroidal drugs (n = 2) and healthy subjects (n = 1) (p = 0.571). However, the frequency was significantly higher in patients using a local steroid. Some authors have suggested that the intensity of mites is important in the disease process.Reference Lacey, Kavanagh and Tseng14 In particular, it was indicated that an intensity greater than five mites per cm2 is associated with enhanced pathogenicity.Reference Baima and Sticherling15 It has been reported that mites also behave as a carrier for micro-organisms (streptococci and staphylococci).Reference Liu, Sheha and Tseng10
A potential pathophysiological mechanism of mites in disease development is the hyperplasia and hyperkeratinisation they cause by mechanically occluding fat canals and hair follicles.Reference Pena and Andrade Filho13 In addition, a granulomatous reaction occurs against the chitin exoskeleton of the mite as the mite itself is recognised as a foreign body.Reference Pena and Andrade Filho13 Moreover, a delayed hypersensitivity reaction develops in response to mite debris, which leads to the development of an inflammatory response.Reference Bevins and Liu16
The incidence of demodex species is higher in the faces of rosacea patients when compared with the normal population, and the demodex species has been found to be involved in the aetiology of this condition.Reference Lacey, Kavanagh and Tseng14 It is proposed that demodex species can cause pityriasis folliculorum, perioral dermatitis, scabies-like eruptions, facial pigmentations and eruptions in the scalp.Reference Baima and Sticherling7, Reference Roland and Marple9, Reference Pena and Andrade Filho13 It is implicated in pustular lesions in patients receiving chemotherapy and/or local or systemic steroids, or in patients with immune disorders.Reference Baima and Sticherling7, Reference Roland and Marple9, Reference Pena and Andrade Filho13
• An itchy ear canal is a frequently encountered complaint; its aetiology has not been fully elucidated
• This is the first study on the frequency of demodex species in the external auditory canal
• In this study, the parasite frequency was significantly higher in patients using local steroids
• However, the proportion of patients with demodex-positive samples was small and the clinical significance is unclear
• Demodex species was not significantly higher in patients with an itchy ear canal who were not using local steroids compared with the control group
It has been reported that the incidence of demodex species increases with age.Reference Firat, Geçıt, Depecık, Karadan, Karci and Karaman17, Reference Djalilian and Memar18 Some studies indicate that the mites are not seen in childhood. They appear in puberty and their frequency increases with age, reaching a peak level at advanced ages.Reference Sibenge and Gawkrodger19 Our study revealed no information about the frequency in childhood as patients younger than 18 years of age were excluded. The mean age of patients with demodex species was higher than that of patients without demodex species. The frequency of demodex species rose significantly with increasing age (p = 0.001).
In studies on demodex species, D folliculorum was found in cilia follicles, whereas D brevis was present in the canals of the sebaceous gland.Reference Pena and Andrade Filho13 It has been proposed that the mites spread to the eyes from the face via the eyelids.Reference Pena and Andrade Filho13 It is suggested that the mites can easily spread to the cartilaginous part of the external acoustic meatus, as this is a facial region that also has hair follicles, and sebaceous and apocrine glands.
In conclusion, although family practitioners and ENT clinicians often examine patients complaining of an itchy ear canal, its aetiology has not been fully elucidated. Frequent manipulation of the external acoustic meatus by foreign materials (ear cleaners), and the use of local steroidal drugs for therapeutic purposes, disrupt the defence mechanism and facilitate the spread of infection. Although the rate of demodex species was not significantly higher in patients with itchy ear canals compared with the control group, the use of local steroids increased the parasite frequency in the ear canal. To the best of our knowledge, this is the first study on this subject. However, the proportion of patients with demodex-positive samples was very small and so the clinical significance is unclear. Therefore, further studies with larger patient series may be useful in elucidating this issue.
