Allergies and asthma: They often occur together

James T C Li, M.D., Ph.D.

You may wonder what allergies and asthma have in common besides making you miserable. A lot, as it turns out. Allergies and asthma often occur together.

The same substances that trigger your hay fever (allergic rhinitis) symptoms, such as pollen, dust mites and pet dander, may also cause asthma signs and symptoms. In some people, skin or food allergies can cause asthma symptoms. This is called allergic asthma or allergy-induced asthma.

James T C Li, M.D., Ph.D., a Mayo Clinic allergy specialist, answers questions about the link between allergies and asthma.

How does an allergic reaction cause asthma symptoms?

An allergic response occurs when immune system proteins (antibodies) mistakenly identify a harmless substance, such as tree pollen, as an invader. In an attempt to protect your body from the substance, antibodies bind to the allergen.

The chemicals released by your immune system lead to allergy signs and symptoms, such as nasal congestion, runny nose, itchy eyes or skin reactions. For some people, this same reaction also affects the lungs and airways, leading to asthma symptoms.

Are allergies and asthma treated differently?

Most treatments are designed to treat either asthma or allergic rhinitis. But a few treatments help with both conditions. Some examples:

• Leukotriene modifier. This type of medication can ease both allergic rhinitis and asthma symptoms. Called a leukotriene modifier, this daily pill helps control immune system chemicals released during an allergic reaction. Montelukast (Singulair) is the leukotriene modifier that can treat both asthma and allergic rhinitis.

• Allergy shots (immunotherapy). Allergy shots can help treat asthma by gradually reducing your immune-system response to certain allergy triggers. Immunotherapy involves getting regular injections of a tiny amount of the allergens that trigger your symptoms.

  Your immune system builds up a tolerance to the allergens over time, and your allergic reactions diminish. In turn, asthma symptoms decrease as well. This treatment generally requires regular injections over a period of time.

• Anti-immunoglobulin E (IgE) therapy. When you have an allergy, your immune system mistakenly identifies a specific substance as something harmful and releases antibodies, known as IgE, against the culprit allergen.

  The next time you encounter that allergen, the IgE antibodies sense it and signal your immune system to release a chemical called histamine, as well as other chemicals, into your bloodstream. The medication omalizumab (Xolair) interferes with IgE in the body and helps prevent the allergic reaction that triggers asthma symptoms. This treatment is used for more severe allergic asthma, but it might also help allergic rhinitis.

You may need other medications to treat allergies or asthma, especially if your symptoms become severe at times. However, recognizing and avoiding the substances that trigger your symptoms is an important step you can take.

Who's at risk of allergic asthma?

A family history of allergies is a major risk factor for allergic asthma. Having hay fever or other allergies yourself also increases your risk of getting asthma.

Is all asthma caused by allergies?

Though allergic asthma is very common, there are other types of asthma with different kinds of triggers. For some people, asthma can be triggered by exercise, infections, cold air, gastroesophageal reflux disease or stress. Many people have more than one kind of asthma trigger.

Take charge: Get symptoms under control

Know the things that trigger your allergy and asthma symptoms and learn how to limit your exposure to them. Work with your doctor to find the best treatment to manage your symptoms, and check in with your doctor on a regular basis.

Because allergy and asthma symptoms can change over time, you may need to adjust your treatment accordingly. Learn the signs that your asthma may be flaring up — and know what to do when it does.