Allergic skin reactions are very common, and it can be difficult to figure out what causes them. There are hundreds of different kinds of rashes that can be caused by many things, such as plants like poison ivy, allergic reactions to a medication or a food, or a response to an illness.
Allergic eczema (atopic dermatitis) and hives (urticaria) are two of the most common skin rashes. Eczema affects 10 percent to 20 percent of children and 1 percent to 3 percent of adults. If you have eczema, your skin may become red, irritated and itchy. Sometimes there are small, fluid-filled bumps that ooze.
Hives are red bumps or welts that appear on the body. About 20 percent of Americans have hives at some time in their lives.
Contact dermatitis is caused when the skin touches either an allergen or something that irritates it, causing symptoms such as a rash, blisters, itching and burning. Most cases of contact dermatitis are not caused by an allergen but by something that irritates the skin such as soap, detergents and some plants.