Individuals with allergic contact dermatitis (see the image below) may have persistent or relapsing dermatitis, particularly if the material(s) to which they are allergic is not identified or if they practice inappropriate skin care. The longer an individual has severe dermatitis, the longer, it is believed, that the dermatitis will take to resolve once the cause is identified.
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.
Signs and symptoms
Acute allergic contact dermatitis is characterized by pruritic papules and vesicles on an erythematous base. Lichenified pruritic plaques may indicate a chronic form of the condition.
Individuals with allergic contact dermatitis typically develop the condition within a few days of exposure, in areas that were exposed directly to the allergen. Certain allergens (eg, neomycin), however, penetrate intact skin poorly; in such cases, the onset of dermatitis may be delayed for up to a week following exposure.
Individuals may develop widespread dermatitis from topical medications applied to leg ulcers or from cross-reacting systemic medications administered intravenously.
Intraoral metal contact allergy may result in mucositis that mimics lichen planus, which has an association with intraoral squamous cell carcinoma.
See Clinical Presentation for more detail.
Diagnostic studies for allergic contact dermatitis include the following:
- Potassium hydroxide preparation and/or fungal culture: To exclude tinea; these tests are often indicated for dermatitis of the hands and feet
- Patch testing: To identify external chemicals to which the person is allergic
- Repeat open application test (ROAT): To determine whether a reaction is significant in individuals who develop weak or 1+ positive reactions to a chemical
- Dimethylgloxime test: To determine whether a metallic object contains enough nickel to provoke allergic dermatitis
- Skin biopsy: May help to exclude other disorders, particularly tinea, psoriasis, and cutaneous lymphoma
See Workup for more detail.
The definitive treatment for allergic contact dermatitis is the identification and removal of any potential causal agents; otherwise, the patient is at increased risk for chronic or recurrent dermatitis. Treatments also include the following:
- Corticosteroids: Topical corticosteroids are the mainstay of treatment, although acute, severe allergic contact dermatitis, such as from poison ivy, often needs to be treated with a 2-week course of systemic corticosteroids
- Topical immunomodulators (TIMs): Approved for atopic dermatitis, but they are also prescribed for cases of allergic contact dermatitis when they offer safety advantages over topical corticosteroids
- Phototherapy: Administered to individuals with chronic allergic contact dermatitis that is not controlled well by topical corticosteroids; these patients may benefit from treatment with a combination of psoralen (a photosensitizer) and ultraviolet-A (PUVA)
- Immunosuppressive agents: Chronic immunosuppressive agents are, in rare instances, used to treat recalcitrant cases of severe, chronic, widespread allergic contact dermatitis or severe hand dermatitis that prevents a patient from working or performing daily activities
- Disulfiram: Occasionally, an individual who is highly allergic to nickel and has severe vesicular hand dermatitis will benefit from treatment with disulfiram (Antabuse); the drug has a chelating effect