While asthma is a lung disease that causes breathing difficulty, it is often part of a larger syndrome called atopy. This term refers to an increased tendency to develop allergic reactions. People who are atopic can present with a variety of allergic disorders, including nasal allergies, allergic asthma and allergic rashes. Types of allergic rashes someone with allergic asthma might experience include atopic dermatitis, atopic urticaria and allergic contact dermatitis.
Also known as eczema, atopic dermatitis refers to a red, itchy rash commonly found on the cheeks in infants and in the creases of the elbows and knees in older children and adults. Most people with atopic dermatitis have generalized dry skin, and a cycle can emerge of itchy, dry skin that becomes even more itchy when scratched. Further scratching worsens the rash, continuing the cycle. With mild to moderate atopic dermatitis, the rash comes and goes. Severe eczema is often more persistent, leading to long-term skin changes caused by the itch-scratch cycle. Not all people with atopic dermatitis develop asthma, but it does increase the risk. A September 2007 "Journal of Allergy and Clinical Immunology" research review reported that one out of three children with atopic dermatitis develop asthma.
Urticaria, or hives, are intensely itchy white lumps surrounded by bright pink or red skin. They often appear quickly and can move to different areas of the body. Hives typically disappear in less than 24 hours, leaving skin appearing normal. Exposure to a substance the affected person is allergic to -- an allergen -- triggers a cascade of chemical reactions that culminate in the emergence of hives. Common allergic triggers include food, insect bites and drug allergies. At least 50 percent of people with asthma have the allergic type, according to the 2014 findings of a National Institutes of Health-convened asthma task force. Given that atopic urticaria and allergic asthma share a common biochemical and immune system basis, it's not surprising that both conditions can occur in the same person.
Allergic Contact Dermatitis
Allergic contact dermatitis is another form of allergic skin reaction. The area touched by an allergen develops a rash that is usually red and itchy. There may be blisters that ooze or develop a crust. Nickel is the most common cause of allergic contact dermatitis, often found in jewelry or in the metal buttons on pants. A study published in July 2014 in the "Journal of Investigative Dermatology" found a specific biochemical link between allergic contact dermatitis and asthma. A chemical produced by immune system cells called cytokine IL-9 has been found in high levels in people with allergic asthma. The same chemical was found in higher levels in people with allergic contact dermatitis caused by nickel allergy than in people with skin not reactive to nickel.
Avoidance and Treatment
The first step in treating any allergic disease is to remove or avoid the allergens. For example, avoiding foods known to trigger symptoms, buying nickel-free jewelry or placing a piece of tape over the inside surface of a nickel-containing button on pants may help prevent allergic skin symptoms from recurring. A central tenet of preventing symptom flareups with atopic dermatitis is preventing skin dryness with aggressive moisturizing. Topical steroids may be helpful in persistent cases of atopic dermatitis and allergic contact dermatitis, and oral antihistamines are often very effective for short-term relief of atopic urticaria.
Warnings and Precautions
Allergic reactions can range in severity from mild to life-threatening, and they can occur very quickly. Any allergic reaction that results in swelling of the tongue, lips, or throat can affect the ability to breathe and is a medical emergency. Seek care immediately. The rashes described may be related to asthma, but there are many other kinds of rashes a person with asthma can experience as well. Have any new rash checked out by a healthcare provider, particularly if it is worsening, spreading, or is associated with fever, joint pain or other symptoms.
Medical advisor: Shilpi Agarwal, M.D.