Allergies may be the underlying cause of a variety of skin rashes. These include hives, contact rashes and eczema.
- Hives are raised, red, itchy welts on the skin. Allergies to food, antibiotics, soaps and cosmetics, insect bites and environmental allergens such as animal danders can cause hives. Non-allergic factors such as pressure on the skin, heat, hormonal abnormalities, infections and arthritis can also produce hives.
A medical evaluation is important to determine the cause of hives, which are medically termed “urticaria.” Skin and blood tests and a thorough history and examination can help identify whether the hives are allergic in nature.
Allergic hives respond to avoiding offending foods, drugs, or environmental allergens. Allergy shots are effective in certain cases.
- Contact rashes appear as itchy scales and blisters which sometimes ooze. Contact dermatitis is often due to sensitivity to metals such as the nickel alloy in jewelry, to the chemicals in cosmetics and industrial materials, and to plants such as poison ivy or poison oak..
Rash location may be a clue to the cause. For example, foot rashes may be due to sensitivity to chemicals in leather shoes. Rashes on the wrist can be caused by allergy to nickel in wrist watches or bracelets.
Patch skin testing in one way to identify these sensitivities, which are causes by cellular reactions rather than allergic antibodies. Allergy shots are not effective for these types of reactions; avoiding contact and using anti-inflammatory steroid creams are the main treatments for contact rashes.
- Eczema is characterized by an itchy, scaling red rash which is distributed over certain parts of the skin. Infants have this rash on their cheeks, while adults have it behind their knees, on the insides of the elbows and wrists, and on their necks.