Summary

• Irritant contact dermatitis is caused by direct toxicity without prior sensitisation, and allergic contact dermatitis is a delayed hypersensitivity reaction.
• Results in localised burning, stinging, itching, blistering, redness, and swelling at the area of contact with the allergen or irritant.
• Patch testing may aid identification of the offending agent. Skin biopsy may also be helpful, but may not be able to distinguish between other causes of dermatitis.
• Treatment involves removal of the offending agent, future avoidance of the offending agent, topical corticosteroids, and/or a short course of oral corticosteroids.
• Rarely, contact dermatitis can become generalised, leading to areas of dermatitis in locations distant from the site of contact with the offending agent.
• Other allergic conditions may be triggered by exposure to an allergen, such as allergic rhinitis, asthma, and anaphylaxis.