Why does contact dermatitis cause skin rash?

Irritant contact dermatitis develops when a substance damages the skin barrier. Allergic contact dermatitis involves an immune response to a substance the skin has become sensitive to. Either type can cause redness, itching, dryness, swelling, weeping, or a rough surface. The rash may follow the outline of an object, appear where a product was applied, or extend beyond the original contact area. Timing matters: a clinician may ask about new soaps, fragrances, hair products, jewellery, plants, gloves, or medicines.

Pause products that may have touched the rash and gently wash away residue with lukewarm water. Avoid scratching, scrubbing, and fragranced creams. A cool compress can ease itch and heat; a bland moisturiser may support the barrier when the surface is intact. Do not apply leftover prescription medicine to a new rash without advice, especially on the face, skin folds, or near the eyes. Photograph changes and list recent exposures for your appointment.

Arrange an assessment if the rash is spreading, recurrent, very uncomfortable, blistered, or not improving after the suspected trigger is removed. Seek prompt care for pus, increasing warmth, swelling, pain, fever, or rapidly worsening skin. Emergency help is needed if the rash comes with trouble breathing, faintness, or swelling of the lips, mouth, or tongue.

Does the distribution suggest a contact trigger? Which ingredients should I avoid while the skin heals? Would patch testing be useful, and what treatment is suitable for this body area?