Contact Dermatitis
Contact dermatitis is skin inflammation from direct contact with an irritant or allergen, split into irritant (about 80% of cases) and allergic types, per current disease primers.
Symptoms
Redness, itching, and sometimes blistering at the site of contact -- irritant reactions can appear within hours, while allergic reactions typically take 12-48 hours to develop after exposure.
Causes and risk
Irritant contact dermatitis comes from repeated exposure to mild irritants (soaps, frequent hand-washing, solvents); allergic contact dermatitis is a true immune reaction to a specific allergen (nickel, fragrance, poison ivy, certain preservatives).
How it is evaluated
Patch testing identifies the specific allergen in persistent or unclear cases: patches are applied for 48 hours with readings at removal and again at day 7, per European Society of Contact Dermatitis best-practice guidance.
Treatment
Avoiding the trigger is the essential first step. Emollients and topical corticosteroids are the mainstay, used cautiously on thin skin; calcineurin inhibitors are steroid-sparing alternatives. Extensive reactions (like widespread poison ivy) may need a 2-3 week oral steroid taper -- shorter courses risk a rebound flare.
When to seek care
Contact with a strong acid or alkali can cause a chemical burn requiring emergency (burn-style) management, not routine dermatitis care. Facial or airway swelling needs immediate attention.