Brief Reports
Allergic Contact Dermatitis from the Earmolds of Hearing Aids Birgitta Meding, PhD, MD; Anders Ringdahl, PhD, MD Departments of Dermatology, Audiology, and Otolaryngology, Sahlgrenska Sjukhuset, Goteborg, Sweden (8.M., A.R.) and the Department of Occupational Dermatology, National lnstitute of Occupational Health, Solna, Sweden (8.M.)
ABSTRACT Hearing aid users with longstanding and severe dermatitis in the ear canal were examined by a dermatologist and patch tested. In 6 of 22 (27%) patients, contact allergy to the earmold material was found. Four of the six had a positive test reaction to methyl methacrylate and two also to triethyleneglycol dimethacrylate and urethane dimethacrylate. Positive patch test reactions to substances used for topical treatment were found as well. Routines including liberal patch testing for this group of patients are suggested. (Ear Hear 13 2:122-124)
IN SWEDEN, ABOUT 200,000 persons use hearing aids. The hearing aid is connected to the ear canal by an earmold. Imtation, itching, and discharge from the auditory meatus and the external ear canal is a problem that sometimes makes use of the hearing aid difficult or even impossible. Skin imtation due to occlusion is the most common cause. Sometimes there is an activation of a latent skin disease such as psoriasis or seborrheic dermatitis. In some cases, the cause of the problem is contact allergy to the mold material. Earmolds are of two types, hard and soft. The most common materials are methacrylic plastics, but polyvinyl chloride or silicone is sometimes used. The methacrylic plastics are polymerization products of methyl methacrylate (MMA) or some other methacrylate monomer [e.g., ethyleneglycol dimethacrylate (EGDMA)]. The curing process is either performed by cold curing, which leaves about 3% of the monomer uncured, or by heat curing, leaving 0.2% of residual monomer, or even less if done properly. The first choice for a new hearing aid user in Sweden is often a hard, cold-cured acrylic earmold. Other substances used in the manufacturing process include phtalates as plasticizers, benzoylperoxide as an initiator, and hydroquinone and aromatic amines as inhibitors. 122
Meding and Ringdahl
There are occasional case reports on contact allergy to hearing aids and earmolds. Attrup Rasmussen (1974) reported one patient with a positive patch test to a hearing Ad insert without specifying the type of material. Jordan and Dahl(l972) had one patient who was allergic to cellulose ester plastics (resorcinol), and Fisher (198 1) saw one case of vinyl plastics allergy. Guill and Odom ( 1978) reported one case caused by MMA in an in the ear hearing aid, and Cockerill (1987) found 14 cases allergic to MMA, one to vulcanite, and two to polyvinyl chloride. Recently, one patient allergic to an ultraviolet-cured prepolymer used in earmold manufacture and consisting of acrylated urethane oligomer and methacrylated urethane, was reported by Dutree-Meulenberg, Naafs, van Joost, and Geursen-Reitsma (199 1). Pigatto, Bigardi, Legori, Altomare, and Troiano ( 1991) studied the prevalence of allergic contact dermatitis in 64 subjects with otitis externa and found two patients allergic to MMA. The aim of the present study was to investigate the occurrence of contact allergy to earmold materials in hearing aid users with severe dermatitis in the ear canal. MATERIAL AND METHODS
Twenty-two hearing aid users, four males and 18 females, with longstanding and severe dermatitis in the ear canal, making the use of the hearing aid impossible, were referred from the Department of Audiology for dermatological examination and patch testing. The mean age of the patients was 65.8 yr, ranging from 25 to 83. The patients were very dependent on hearing aids, as the average hearing impairment at the frequencies 0.5, 1.0, and 2.0 kHz was 59 dB HL in the better ear. Patch Testing Patch testing was performed with the standard series recommended by the Swedish Contact Dermatitis Group and also with a plastics series of six different methacrylate monomers, each diluted 2% in petrolatum (see Table 2), with 27 other plastics chemicals and with scrapings from the patients’ own earmolds and some standard molds. The test substances, except for the earmold scrapings, were obtained from Chemotechnique Diagnostics AB (Malmo, Sweden). Finn Chambers (Epitest Ltd., Oy, Finland) and Scanpore tape (Norgesplaster, Norway) were used. The test patches were removed after 48 hr and the reactions were assessed 72 hr after application and scored according to Fregert (1981) (Tables 1 and 2).
0196/0202/92/1302-0122$03.00/0 * EARAND HEARING Copyright Q 1992 by Williams & Wilkins
Printed in the U.S.A.
Ear and Hearing, Vol. 13, No. 2,1992
Table 1. Positive patch test reactions to the standard series in 22 patients. Conc.
[“4
Substance Nickel sulphate Fragrance mix Caine mix Amerchol L 101 Neomycin sulphate Quinoline mix Thiuram mix Black rubber mix Ethylenediamine dihydrochloride
5 8 3 100 20 6 1 0.6 1
Vehicle
n
peta Pet Pet
5 2 2
Pet Pet Pet Pet Pet
1 1 1 1
1 1
“pet = petrolatum.
Table 2. Patch test results to methacrylates in 22 patients. The test concentrationfor each substance was 2% in petrolatum. Substance
n
MMA (methyl methacrylate) TREGDMA (triethyleneglycol dimethacrylate) UEDMA (urethane dimethacrylate) EGDMA (ethyleneglycol dimethacrylate) BIS-GMA” BIS-MAb
4
~
2 2
~~~~
BIS-GMA, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy]phenylpropane. BIS-MA, 2,2-bis[4-(methacryloxy)phenyl]propane. a
RESULTS
In nine patients, 15 positive test reactions to substances in the standard series were found (Table 1). Several of the reactions were to substances used in topical remedies (e.g., Amerchol L 101, neomycin sulphate, quinoline mix, ethylenediamine dihydrochloride, and caine mix). In six patients (27%), contact allergy to the mold material was diagnosed. Five of them had positive reactions to scrapings from the earmolds. Four of the six showed positive tests to MMA, and two of these were also positive to EGDMA and TREGDMA (Table 2). For the other plastics chemicals, only one positive reaction, to phenol formaldehyde resin (1% petrolatum), was found. The diagnoses given at the dermatological examination were allergic contact dermatitis in seven cases and seborrheic dermatitis in another six. In the remaining nine patients, the diagnosis was not so obvious, although irritation from occlusion was probable. DISCUSSION
In six of these 22 patients, contact allergy to the earmold material appeared to be the cause of their symptoms. Methyl methacrylate is a well-known sensitizer (Fisher, 1986). Only a few cases are, however, reported concerning contact allergy to methacrylates in Ear and Hearing, Vol. 13, No. 2,1992
earmolds. Cockerill ( 1987), however, who used more or less the same selection procedure as in the present study, found a true allergic reaction to MMA in 14 out of 25 hearing aid users with otitis externa. The occlusive conditions in the ear canal favor sensitization to mold material as well as to substances used for topical treatment. It is probable that many cases are not being correctly diagnosed, as the patients are not referred to dermatologists for patch testing. There are no fixed rules on how to handle severe external otitis in hearing aid users at Swedish hearing centers. The most common way to solve the problems is to make another mold containing less monomer. Finally, the patient may get a silicone mold. This routine has at least two disadvantages. First, the soft silicone mold has to be remade about every other year, and second, the tubing cannot be glued to the mold. An unknown number of patients are unnecessarily prescribed a silicone mold. An early and correct diagnosis would be advantageous to the patient with contact dermatitis to MMA and to the patient with severe external otitis from occlusion of the external ear canal. The first group would get a silicone mold at an early stage and the second would get the correct choice of hearing aid prescription (e.g., a bone-anchored hearing aid) (Hikansson, LidCn, Tjellstrom, Ringdahl, Jacobsson, Carlsson, & Erlandsson 1990). From the results of the present study, no conclusion is possible on the prevalence of contact allergy to earmold material, as the patients were selected cases with longstanding and severe symptoms. In two of the cases with positive reactions to scrapings from earmolds, it was not possible to find the allergen. It was difficult to get information on the composition of the materials used in the molds. Routines for cooperation regarding investigation and treatment of patients with contact dermatitis should be established between the departments of audiology and dermatology. Ear, nose, and throat specialists are recommended to send hearing-impaired patients with longstanding inflammation of the ear canal to departments of dermatology for patch testing. The audiologist can, thus, select the appropriate treatment at an early stage. The audiologist should also be aware of the possibility of contact dermatitis developing due to sensitization to mold material and to remedies used for treatment.
REFERENCES Attrup Rasmussen P. Otitis externa and allergic contact dermatitis. Acta Otolaryngol 1974;77:344-347. Cockerill D. Allergies to ear moulds. Br J Audio1 1987;21:143-145. Dutree-Meulenberg ROGM, Naafs B, van Joost Th, and GeursenReitsma AM. Contact dermatitis caused by urethane acrylates in a hearing aid. Contact Dermatitis 1991;24:143-145. Fisher AA. Allergen replacement (alternatives) in the management of contact dermatitis. Cutis 1981;28:368-372. Fisher AA. Contact Dermatitis, 3rd ed. Philadelphia: Lea & Febiger, 1986~555-559. Fregert S. Manual of Contact Dermatitis, 2nd ed. Copenhagen: Munksgaard, 1981.
Allergic Contact Dermatitis from Earmolds
123
Guill MA and Odom RB. Hearing aid dermatitis. Arch Dermatol l978;114: 1050-105 1. Hikansson B, Liden G, Tjellstrom A, Ringdahl A, Jacobson M, Carlsson P, and Erlandsson BE. Ten years of experience of the Swedish bone-anchored system. Ann Otol Lawngo] 1990;99(suppl 151 ):2. Jordan WP and Dahl MV. Contact dermatitis from cellulose ester plastics. Arch Dermatol 1972: L05:880-885. Pigatto PD, Bigardi A, Legori A, Altornare G, and Troiano L. Allergic
124
Meding and Ringdahl
contact dermatitis prevalence in patients with otitis externa. Acta Derm Venereol (Stockh) 1991;71:162-l65. Address reprint requests to ~ i ~ Meding, ~ i t t Department ~ of Occupational Dermatology, National Institute of Occupational Health, S-171 84 Solna, Sweden. Received October 6, 1991: accepted October 30, 1991
Ear and Hearing, Vol. 13, No. 2,1992
Allergic Contact Dermatitis from the Earmolds of Hearing Aids Birgitta Meding, PhD, MD; Anders Ringdahl, PhD, MD Departments of Dermatology, Audiology, and Otolaryngology, Sahlgrenska Sjukhuset, Goteborg, Sweden (8.M., A.R.) and the Department of Occupational Dermatology, National lnstitute of Occupational Health, Solna, Sweden (8.M.)
ABSTRACT Hearing aid users with longstanding and severe dermatitis in the ear canal were examined by a dermatologist and patch tested. In 6 of 22 (27%) patients, contact allergy to the earmold material was found. Four of the six had a positive test reaction to methyl methacrylate and two also to triethyleneglycol dimethacrylate and urethane dimethacrylate. Positive patch test reactions to substances used for topical treatment were found as well. Routines including liberal patch testing for this group of patients are suggested. (Ear Hear 13 2:122-124)
IN SWEDEN, ABOUT 200,000 persons use hearing aids. The hearing aid is connected to the ear canal by an earmold. Imtation, itching, and discharge from the auditory meatus and the external ear canal is a problem that sometimes makes use of the hearing aid difficult or even impossible. Skin imtation due to occlusion is the most common cause. Sometimes there is an activation of a latent skin disease such as psoriasis or seborrheic dermatitis. In some cases, the cause of the problem is contact allergy to the mold material. Earmolds are of two types, hard and soft. The most common materials are methacrylic plastics, but polyvinyl chloride or silicone is sometimes used. The methacrylic plastics are polymerization products of methyl methacrylate (MMA) or some other methacrylate monomer [e.g., ethyleneglycol dimethacrylate (EGDMA)]. The curing process is either performed by cold curing, which leaves about 3% of the monomer uncured, or by heat curing, leaving 0.2% of residual monomer, or even less if done properly. The first choice for a new hearing aid user in Sweden is often a hard, cold-cured acrylic earmold. Other substances used in the manufacturing process include phtalates as plasticizers, benzoylperoxide as an initiator, and hydroquinone and aromatic amines as inhibitors. 122
Meding and Ringdahl
There are occasional case reports on contact allergy to hearing aids and earmolds. Attrup Rasmussen (1974) reported one patient with a positive patch test to a hearing Ad insert without specifying the type of material. Jordan and Dahl(l972) had one patient who was allergic to cellulose ester plastics (resorcinol), and Fisher (198 1) saw one case of vinyl plastics allergy. Guill and Odom ( 1978) reported one case caused by MMA in an in the ear hearing aid, and Cockerill (1987) found 14 cases allergic to MMA, one to vulcanite, and two to polyvinyl chloride. Recently, one patient allergic to an ultraviolet-cured prepolymer used in earmold manufacture and consisting of acrylated urethane oligomer and methacrylated urethane, was reported by Dutree-Meulenberg, Naafs, van Joost, and Geursen-Reitsma (199 1). Pigatto, Bigardi, Legori, Altomare, and Troiano ( 1991) studied the prevalence of allergic contact dermatitis in 64 subjects with otitis externa and found two patients allergic to MMA. The aim of the present study was to investigate the occurrence of contact allergy to earmold materials in hearing aid users with severe dermatitis in the ear canal. MATERIAL AND METHODS
Twenty-two hearing aid users, four males and 18 females, with longstanding and severe dermatitis in the ear canal, making the use of the hearing aid impossible, were referred from the Department of Audiology for dermatological examination and patch testing. The mean age of the patients was 65.8 yr, ranging from 25 to 83. The patients were very dependent on hearing aids, as the average hearing impairment at the frequencies 0.5, 1.0, and 2.0 kHz was 59 dB HL in the better ear. Patch Testing Patch testing was performed with the standard series recommended by the Swedish Contact Dermatitis Group and also with a plastics series of six different methacrylate monomers, each diluted 2% in petrolatum (see Table 2), with 27 other plastics chemicals and with scrapings from the patients’ own earmolds and some standard molds. The test substances, except for the earmold scrapings, were obtained from Chemotechnique Diagnostics AB (Malmo, Sweden). Finn Chambers (Epitest Ltd., Oy, Finland) and Scanpore tape (Norgesplaster, Norway) were used. The test patches were removed after 48 hr and the reactions were assessed 72 hr after application and scored according to Fregert (1981) (Tables 1 and 2).
0196/0202/92/1302-0122$03.00/0 * EARAND HEARING Copyright Q 1992 by Williams & Wilkins
Printed in the U.S.A.
Ear and Hearing, Vol. 13, No. 2,1992
Table 1. Positive patch test reactions to the standard series in 22 patients. Conc.
[“4
Substance Nickel sulphate Fragrance mix Caine mix Amerchol L 101 Neomycin sulphate Quinoline mix Thiuram mix Black rubber mix Ethylenediamine dihydrochloride
5 8 3 100 20 6 1 0.6 1
Vehicle
n
peta Pet Pet
5 2 2
Pet Pet Pet Pet Pet
1 1 1 1
1 1
“pet = petrolatum.
Table 2. Patch test results to methacrylates in 22 patients. The test concentrationfor each substance was 2% in petrolatum. Substance
n
MMA (methyl methacrylate) TREGDMA (triethyleneglycol dimethacrylate) UEDMA (urethane dimethacrylate) EGDMA (ethyleneglycol dimethacrylate) BIS-GMA” BIS-MAb
4
~
2 2
~~~~
BIS-GMA, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy]phenylpropane. BIS-MA, 2,2-bis[4-(methacryloxy)phenyl]propane. a
RESULTS
In nine patients, 15 positive test reactions to substances in the standard series were found (Table 1). Several of the reactions were to substances used in topical remedies (e.g., Amerchol L 101, neomycin sulphate, quinoline mix, ethylenediamine dihydrochloride, and caine mix). In six patients (27%), contact allergy to the mold material was diagnosed. Five of them had positive reactions to scrapings from the earmolds. Four of the six showed positive tests to MMA, and two of these were also positive to EGDMA and TREGDMA (Table 2). For the other plastics chemicals, only one positive reaction, to phenol formaldehyde resin (1% petrolatum), was found. The diagnoses given at the dermatological examination were allergic contact dermatitis in seven cases and seborrheic dermatitis in another six. In the remaining nine patients, the diagnosis was not so obvious, although irritation from occlusion was probable. DISCUSSION
In six of these 22 patients, contact allergy to the earmold material appeared to be the cause of their symptoms. Methyl methacrylate is a well-known sensitizer (Fisher, 1986). Only a few cases are, however, reported concerning contact allergy to methacrylates in Ear and Hearing, Vol. 13, No. 2,1992
earmolds. Cockerill ( 1987), however, who used more or less the same selection procedure as in the present study, found a true allergic reaction to MMA in 14 out of 25 hearing aid users with otitis externa. The occlusive conditions in the ear canal favor sensitization to mold material as well as to substances used for topical treatment. It is probable that many cases are not being correctly diagnosed, as the patients are not referred to dermatologists for patch testing. There are no fixed rules on how to handle severe external otitis in hearing aid users at Swedish hearing centers. The most common way to solve the problems is to make another mold containing less monomer. Finally, the patient may get a silicone mold. This routine has at least two disadvantages. First, the soft silicone mold has to be remade about every other year, and second, the tubing cannot be glued to the mold. An unknown number of patients are unnecessarily prescribed a silicone mold. An early and correct diagnosis would be advantageous to the patient with contact dermatitis to MMA and to the patient with severe external otitis from occlusion of the external ear canal. The first group would get a silicone mold at an early stage and the second would get the correct choice of hearing aid prescription (e.g., a bone-anchored hearing aid) (Hikansson, LidCn, Tjellstrom, Ringdahl, Jacobsson, Carlsson, & Erlandsson 1990). From the results of the present study, no conclusion is possible on the prevalence of contact allergy to earmold material, as the patients were selected cases with longstanding and severe symptoms. In two of the cases with positive reactions to scrapings from earmolds, it was not possible to find the allergen. It was difficult to get information on the composition of the materials used in the molds. Routines for cooperation regarding investigation and treatment of patients with contact dermatitis should be established between the departments of audiology and dermatology. Ear, nose, and throat specialists are recommended to send hearing-impaired patients with longstanding inflammation of the ear canal to departments of dermatology for patch testing. The audiologist can, thus, select the appropriate treatment at an early stage. The audiologist should also be aware of the possibility of contact dermatitis developing due to sensitization to mold material and to remedies used for treatment.
REFERENCES Attrup Rasmussen P. Otitis externa and allergic contact dermatitis. Acta Otolaryngol 1974;77:344-347. Cockerill D. Allergies to ear moulds. Br J Audio1 1987;21:143-145. Dutree-Meulenberg ROGM, Naafs B, van Joost Th, and GeursenReitsma AM. Contact dermatitis caused by urethane acrylates in a hearing aid. Contact Dermatitis 1991;24:143-145. Fisher AA. Allergen replacement (alternatives) in the management of contact dermatitis. Cutis 1981;28:368-372. Fisher AA. Contact Dermatitis, 3rd ed. Philadelphia: Lea & Febiger, 1986~555-559. Fregert S. Manual of Contact Dermatitis, 2nd ed. Copenhagen: Munksgaard, 1981.
Allergic Contact Dermatitis from Earmolds
123
Guill MA and Odom RB. Hearing aid dermatitis. Arch Dermatol l978;114: 1050-105 1. Hikansson B, Liden G, Tjellstrom A, Ringdahl A, Jacobson M, Carlsson P, and Erlandsson BE. Ten years of experience of the Swedish bone-anchored system. Ann Otol Lawngo] 1990;99(suppl 151 ):2. Jordan WP and Dahl MV. Contact dermatitis from cellulose ester plastics. Arch Dermatol 1972: L05:880-885. Pigatto PD, Bigardi A, Legori A, Altornare G, and Troiano L. Allergic
124
Meding and Ringdahl
contact dermatitis prevalence in patients with otitis externa. Acta Derm Venereol (Stockh) 1991;71:162-l65. Address reprint requests to ~ i ~ Meding, ~ i t t Department ~ of Occupational Dermatology, National Institute of Occupational Health, S-171 84 Solna, Sweden. Received October 6, 1991: accepted October 30, 1991
Ear and Hearing, Vol. 13, No. 2,1992
