The most general skin allergies contain contact allergic dermatitis and urticarial reactions (hives). Contact allergic dermatitis can have a variety of presentations, mostly commonly appearing as red, scaly itchy marks that can blister and weep in severe cases. The distribution of this rash on the body can often give clues regarding its underlying reason. There are many other allergens that reason contact dermatitis and certain occupations such as hairdressers and nurses are at enlarged risk of developing these reactions.
Another common contact allergen is the preservative Methylchloroisothiozolinone (MCI) and Methylisothiozolinone (MI), also sometimes referred to as Kathon. This allergen is a preservative found in many bathroom products including shampoos, conditioners, washes, wet wipes, cosmetics, sunscreens and moisturizing creams. Some paints also contain this preservative. Patch testing is the formal method of allergy testing for contact allergic dermatitis. The repeat open application test (ROAT) is a self-directed way of testing a product/allergen to see whether you react. This involves applying a small amount of a suspect product on the inner forearm twice daily for a week to see whether an itchy rash develops.
Something touches your skin, and your immune system thinks it’s under attack. It overreacts and sends antibodies to help fight the invader, called an allergen. The result is a red, itchy rash where the substance landed.