What Is the Difference Between Allergies and Asthma?

Allergies and asthma are different, though they may have related reactions and some of the body's chemicals that are involved in allergies are also involved in asthma. An allergy is an inflammatory reaction or response to a specific substance. Allergic reactions can involve nasal membranes, the eyes, the skin, the tongue, and the breathing passages in severe reactions. Allergy symptoms include an itchy, stuffy, or runny nose, sneezing, itchy, red, or irritated skin, and itchy, burning, or watery eyes.

Asthma is a chronic inflammatory lung (lower respiratory) disease that causes difficulty breathing.

The things that trigger allergies can also trigger asthma attacks. Allergy symptoms may be a sign of irritants in the air that can provoke asthma symptoms, and allergy attacks can lead to asthma attacks. With both allergies and asthma, people's immune systems react to fight off the allergens (the material that sets off the reaction). The resulting inflammation causes the airways in people with asthma to become significantly narrowed. The swelling that is called inflammation comes from increased mucus and an increased number of white blood cells in the walls of the air passages. In addition, the air passages are narrowed by the contraction of the muscle that surrounds the lining of the airways. These irritated muscles contract in excess, like a rubber band that closes the air tubes even further.

People with asthma also usually have allergies. About 80% of asthma in children and 50% of asthma in adults is felt to be related to allergies. Hay fever (allergic rhinitis) and sinusitis are quite common in asthma patients.