Do allergies cause asthma? The answer to this question is: yes and no. People who have certain kinds of allergies are more likely to have asthma. Which kind of allergies? Usually, the type of allergies that affect your nose and eyes, causing problems like a runny nose or red, itchy eyes.

Whatever causes an allergic reaction, such as pollen or dust mites, can also trigger asthma symptoms. But not everyone who has allergies develops asthma. And not all cases of asthma are related to allergies.

About 23 million people in the United States have asthma. Of these, about 70% have an allergy to something. Many of these people find their asthma symptoms get worse when they're exposed to certain allergens (things that can cause allergic reactions). Common allergens include dust mites, mold, pollen, and animal dander. Parents who have allergies or asthma often pass along the tendency to have these conditions to their kids.

If you have allergies, your immune system reacts to these allergens as if the allergens were invading the body. To fight the allergen, your immune system produces an antibody called immunoglobulin E (IgE).

When the IgE combines with the allergen, a process is set in motion that results in the release of certain substances in the body. One of the substances released is histamine, which causes allergic symptoms that can affect the eyes, nose, throat, skin, gastrointestinal tract, or lungs. When the airways in the lungs are affected, symptoms of asthma (such as coughing, wheezing, or difficulty breathing) can occur.

The body remembers this reaction, so each time the allergen comes into contact with the body, the same thing can happen. Because of that, allergies can make it difficult for some people to keep their asthma under control.

If you have asthma, it's a good idea to look at whether allergies may be triggering your symptoms. Talk with your doctor about how to identify possible triggers. Your doctor might also recommend a visit to an allergist to help you find out if you're allergic to anything. But even if you are allergic to something — or a whole list of things — it doesn't mean that those allergies are causing your asthma symptoms. It does allow you and your doctor to start investigating the connection, though.

Limiting your exposure to possible allergens may be a big help in controlling your asthma. If you can't completely limit your exposure to something, and you have been shown to be allergic to it, your doctor may recommend allergy shots.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: October 2010