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. Certain environmental and food allergens may aggravate eczema and an allergic evaluation can help delineate these triggers. Management usually includes the avoidance of allergic triggers, the liberal use of skin emollients and frequently topical corticosteroids.
Hives are itchy red bumps or welts that appear on the body. They tend to come and go throughout the day. About 20 percent of Americans have hives at some time in their lives. They often occur as a result of an illness or as an allergic response to an environmental or food allergen. In some difficult situations, a trigger is unfortunately not found. Regardless, hives almost always respond to the use of antihistamines (Benadryl).
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 (i.e. - nickel) but by something that irritates the skin such as soap, detergents and some plants. Contact dermatitis can be evaluated by an allergist using a technique known as “patch testing”, where common allergens are applied to the back and often reveal the inciting trigger.
This information has been provided by the American College of Allergy, Asthma and Immunology