Irritant contact dermatitis is caused by direct toxicity without prior sensitisation, and allergic contact dermatitis is a delayed hypersensitivity reaction.
Results in localised burning, stinging, itching, blistering, redness, and swelling at the area of contact with the allergen or irritant.
Patch testing may aid identification of the causative agent. Skin biopsy may also be helpful, but may not be able to distinguish between other causes of dermatitis.
Treatment involves removal of the causative agent, future avoidance of the causative agent, topical corticosteroids, and/or a short course of oral corticosteroids.
Rarely, contact dermatitis can become generalised, leading to areas of dermatitis in locations distant from the site of contact with the causative agent.
Other allergic conditions may be triggered by exposure to an allergen, such as allergic rhinitis, asthma, and anaphylaxis.
Contact dermatitis is an allergic or irritant skin reaction caused by an external agent.
History and exam
Key diagnostic factors
- occupational history of exposure
- history of atopic dermatitis
- previous episodes of similar dermatitis
- acute onset
- affecting hands and face
- affecting sun-exposed skin
- sparing of non-exposed areas of skin
- vesicles and bullae
- lichenoid lesions
- corrosion or ulceration
- pustules and acneiform lesions
Other diagnostic factors
- social history of exposure
- persistence of symptoms
- erythema multiforme
- cellulitic lesions
- granulomatous lesions
- occupation with frequent exposure to water or caustic material
- atopic dermatitis
1st investigations to order
- patch testing
- repeated open application test (ROAT) or provocative use test (PUT)
Investigations to consider
- skin biopsy
- reflectance confocal microscopy (RCM)
irritant contact dermatitis
allergic contact dermatitis (ACD)
- Atopic dermatitis
- Nummular eczema
- Dyshidrotic eczema
- British Association of Dermatologists' guidelines for the management of contact dermatitis 2017
- European Society of Contact Dermatitis guideline for diagnostic patch testing – recommendations on best practice
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