Contact Dermatitis

Contact dermatitis is inflammation of the skin caused by something it has touched. It typically appears as redness, itching, burning, dryness or small blisters, usually confined to the area that made contact — a shape that follows a product's application area is one of its more recognisable features.

Clinicians distinguish two mechanisms. Irritant contact dermatitis is direct damage from a substance, dose-related, and can happen to anyone given enough exposure — repeated hand washing is the everyday example. Allergic contact dermatitis is an immune response in someone who has become sensitised to a specific molecule; once established it can be triggered by very small amounts and tends to appear a day or two after contact rather than immediately.

• Fragrance components, preservatives and some plant extracts are among the more frequently identified cosmetic triggers.
• The delay in the allergic form is why the culprit is so often mis-identified.
• Patch testing arranged by a dermatologist is the established way to name the specific trigger.

Stopping the suspected product and keeping the routine minimal while skin settles is the usual first step. Reactions that are severe, spreading, weeping, or that keep returning without an obvious cause are a reason to see a doctor rather than to keep experimenting with products.