The precise cause of many childhood skin rashes is unknown. However, the visible characteristics of a rash and its accompanying symptoms can often help pinpoint the cause.

Many types of skin rashes are the result of an allergic reaction, which is an exaggerated response by the immune system to a substance that, in most people, causes no symptoms. Allergens common in children include certain foods (e.g., eggs, milk), pollen, dander, sun exposure, medications and insect bites.

The most common forms of allergic rash include:

• Atopic dermatitis (eczema). Inflammation of the skin caused by allergies. The condition produces rashes that are dry, thickened or scaly in appearance. Atopic dermatitis tends to run in families in which family members have allergic rhinitis or asthma. It is a chronic (ongoing) condition that causes the skin to become very itchy and inflamed with redness. Cracking, oozing, crusting and scaling may also occur.
  
  
• Allergic contact dermatitis. Red, itchy welts which rupture, leak fluid and crust, and end up scaling and cracking. Possible allergens causing allergic contact dermatitis in children include lotions, topical medicines, metals, clothing dyes, medications and powders.
  

  

   
• Hives (urticaria). Elevated patches of often discolored and itchy skin. Allergic urticaria is more common in children than in adults. The immune system overreacts to foods, drugs, insect stings, animal dander, or other substances. Hives can also be caused by conditions other than allergies, such as heat, cold and deep pressure.

  

• Angioedema. Swelling that occurs deep in the skin instead of on its surface, especially around the face, lips and eyes. The welts may also appear on the hands, feet or genitalia. Swelling generally occurs where the skin is tight. They can be red, itchy, painful and swell if irritated. Angioedema may be caused by allergic reactions to such things as animal dander, medications, food and insect bites. This condition can also be caused by non–allergic triggers.

  

• Cercarial dermatitis (swimmer’s itch). Caused by an allergic reaction to infection with parasites. Birds and mammals become infected with these microscopic parasites and then release them into lakes and oceans. Children swimming in water contaminated by the parasites may experience skin tingling, burning or itching.