Contact dermatitis, eczema, and hives are types of skin allergies.
Chemicals are the usual cause of contact dermatitis.
Two examples are the chemicals from poison ivy and cosmetic products. With poison ivy, the reaction to a plant chemical may develop right away, or take a few days to develop. A reaction to poison ivy or to cosmetics may cause redness and swelling, burning, stinging, itching, redness, or blisters. Chemicals in cosmetics and lotions may also cause skin reactions. Most of the reactions caused by skin care products occur on the face, hands, and body, wherever these products are used.