contactdermatitis

Contact dermatitis is an inflammatory skin condition triggered by exposure to external substances. It is commonly divided into irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). ICD results from direct chemical damage to the skin, while ACD is a delayed-type hypersensitivity reaction mediated by T cells in response to an allergen.

Symptoms typically include redness, itching, burning, swelling, and sometimes vesicles or oozing lesions at the site of contact. ICD often appears soon after exposure to the irritant; ACD may require a sensitization period and can recur with re-exposure. Diagnosis relies on history and examination; patch testing can identify specific allergens and is considered the gold standard for ACD. Other skin diseases may mimic contact dermatitis, so differential diagnosis is important.

Common irritants include detergents, solvents, acids, alkalis, metals, soaps, and hand sanitizers. Allergens include nickel, fragrances, rubber additives, preservatives, cosmetics, and plant substances like urushiol from poison ivy. In ICD the damage is due to direct cytotoxic effects; in ACD, exposure to the allergen forms a hapten-protein complex that triggers a T-cell–mediated immune response.

Management focuses on removing or avoiding the offending substance, protecting the skin, and reducing inflammation. Treatments include regular emollients, topical corticosteroids to reduce inflammation, and duration-limited systemic steroids for severe cases. Itching can be treated with antihistamines. Chronic or recurrent disease may require longer-term avoidance strategies and occupational adjustments. Prognosis is generally favorable with avoidance of triggers, but persistent exposure can lead to chronic dermatitis.