Allergic Contact Dermatitis Clinical Presentation Physical Examination
Acute allergic contact dermatitis is characterized by pruritic papules and vesicles on an erythematous base. Lichenified pruritic plaques may indicate chronic allergic contact dermatitis. Occasionally, allergic contact dermatitis may affect the entire integument (ie, erythroderma, exfoliative dermatitis). The initial site of dermatitis often provides the best clue regarding the potential cause of allergic contact dermatitis. Note the following.
Hands
Hands are an important site of allergic contact dermatitis, particularly in the workplace. Common causes of allergic dermatitis on the hands include the chemicals in rubber gloves.
Topical medication sites
Allergic contact dermatitis is frequent in the perianal area as a result of the use of sensitizing medications and remedies (eg, topical benzocaine). Topical medications are also important causes of allergic contact dermatitis in cases of otitis externa. Allergy to chemicals in ophthalmologic preparations may provoke dermatitis around the eyes.
Airborne allergic contact dermatitis
Chemicals in the air may produce airborne allergic contact dermatitis. This dermatitis usually occurs maximally on the eyelids, but it may affect other areas exposed to chemicals in the air, particularly the head and the neck.
Hair dyes
Hair dye—in particular, the component p-phenylenediamine (PPD)—may trigger allergic contact dermatitis. Individuals allergic to hair dyes typically develop the most severe dermatitis on the ears and adjoining face rather than on the scalp.
Stasis dermatitis and stasis ulcers
Individuals with stasis dermatitis and stasis ulcers are at high risk for developing allergic contact dermatitis to topical medications applied to inflamed or ulcerated skin (see the image below). The chronicity of this condition and the frequent occlusion of applied medications contribute to the high risk of allergic contact dermatitis to medicament (eg, neomycin) in these patients.
Individuals may develop widespread dermatitis from topical medications applied to leg ulcers or from cross-reacting systemic medications administered intravenously. For example, a patient allergic to neomycin may develop systemic contact dermatitis if treated with intravenous gentamicin.
Chronic stasis dermatitis with allergic contact dermatitis to quaternium-15, a preservative in moisturizer. Allergic contact dermatitis produces areas of erythema in areas of atrophie blanche and varicose veins.Erythema multiforme
Erythema multiforme (EM) is a severe cutaneous reaction with targetoid lesions that occurs primarily after exposure to certain medications or is triggered by infection, most commonly by herpes simplex virus. Rare cases of EM have been reported after allergic contact dermatitis resulting from exposure to poison ivy,[16]tropical woods, nickel, and hair dye (see the image below).
Erythema multiformelike reaction that developed acutely following hair dying.
Intraoral metal contact allergy may result in mucositis that mimics lichen planus, which has an association with intraoral squamous cell carcinoma. Intraoral squamous cell carcinoma adjacent to a dental restoration containing a metal to which the patient was allergic has been reported.[17]
Allergic contact dermatitis may be a direct trigger for skin ulceration in patients with venous insufficiency. Early diagnosis and treatment of allergic contact dermatitis may prevent the development of venous ulcers.
Complications
Darkly pigmented individuals may develop areas of hyperpigmentation or hypopigmentation from allergic contact dermatitis. Occasionally, they may develop depigmentation at sites of allergic contact dermatitis to certain chemicals.
Occasionally, allergic contact dermatitis is complicated by secondary bacterial infection, which may be treated by the appropriate systemic antibiotic.
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