From the Guidelines
Allergic contact dermatitis presents as an intensely pruritic, erythematous rash with well-demarcated borders that corresponds to the area of allergen exposure, typically developing within 48-72 hours after contact with the allergen and including vesicles, bullae, papules, and edema in acute cases, as described in the 2017 guidelines by the British Association of Dermatologists 1. The rash may include various symptoms such as:
- Intense itching, burning, or stinging at the site
- Vesicles, bullae, papules, and edema in acute cases
- Lichenification, scaling, and fissuring in chronic cases Common locations include:
- Hands
- Face
- Neck
- Any skin area can be affected The distribution pattern often provides clues to the causative agent, such as:
- Linear streaks suggesting plant exposure
- Facial dermatitis indicating cosmetic allergies The condition results from a type IV delayed hypersensitivity reaction where previously sensitized T-cells recognize an allergen and trigger an inflammatory cascade, as explained in the 2014 guidelines for the management of atopic dermatitis 1. Common allergens include:
- Metals (especially nickel)
- Fragrances
- Preservatives
- Rubber compounds
- Topical medications
- Plants like poison ivy Diagnosis is primarily clinical, based on the characteristic appearance and distribution of the rash, along with a detailed exposure history, and patch testing can identify specific allergens, as recommended in the 2017 guidelines by the British Association of Dermatologists 1. It is essential to distinguish allergic contact dermatitis from irritant contact dermatitis, which has a more rapid onset and lacks the immunologic basis, as noted in the 2009 guidelines for the management of contact dermatitis 1.
From the Research
Clinical Presentation of Allergic Contact Dermitis (ACD)
The clinical presentation of ACD can vary, but it is generally characterized by:
- Eczematous dermatitis, which presents with erythema, edema, vesicles, scaling, and intense itch in the acute phase 2
- Non-eczematous clinical forms, such as lichenoid, bullous, and lymphomatosis 2
- Lichenification, which is the most common clinical picture in the chronic phase if the culprit allergen is not found or eliminated 2
- Local skin rash, itchiness, redness, swelling, and lesions 3
- Erythema and scaling with visible borders, itching and discomfort 4
- Acute cases may involve a dramatic flare with erythema, vesicles, and bullae, while chronic cases may involve lichen with cracks and fissures 4
Diagnosis and Treatment
Diagnosis of ACD relies on:
- Clinical presentation 5, 6
- Thorough exposure assessment 5
- Evaluation with techniques such as patch testing and skin-prick testing 5, 6
- Patch testing with suspected allergens 2, 4, 6 Treatment of ACD involves:
- Avoidance of the culprit allergen 2, 3, 6
- Topical and/or systemic corticosteroid therapy 2, 4
- Use of topical corticosteroids to treat exacerbations, but avoiding long-term treatment 6
- Use of databases like Contact Allergen Management Program and Contact Allergen Replacement Database to help patients select products that do not contain allergens to which they are sensitized 6