An asthma trigger is a factor that can decrease lung function and lead to sudden difficulty breathing and other symptoms of an asthma attack. When you are around a trigger, you are at increased risk for an asthma attack. A severe attack may mean you have to go to the hospital.

Some triggers are substances you may be allergic to (allergens). These triggers may include:

• House dust mites.
• Cockroaches.
• Animal dander.
• Indoor mold.
• Pollen.

Other triggers are not allergens-they can cause asthma symptoms, but you are not allergic to them. These include:

• Cigarette smoke and air pollution.
• Upper respiratory infections such as colds, influenza (flu), and sinusitis.
• Exercise. Many people with asthma have symptoms when they exercise.
• Dry, cold air.
• Medicines, such as beta-blockers, aspirin, and other nonsteroidal anti-inflammatory drugs (NSAIDs).
• In adults, hormones, including those involved in pregnancy and menstrual periods. Your symptoms may change just before or during periods.
• Gastrointestinal reflux disease (GERD). Some experts debate whether GERD makes asthma worse. Studies have shown conflicting results as to whether GERD triggers asthma.¹

Identifying asthma triggers helps you know what increases your asthma symptoms. If you avoid triggers, you may be able to:

• Avoid an asthma attack altogether.
• Reduce the length and severity of an asthma attack.

1. Identify possible asthma triggers. A trigger is anything that can lead to an asthma attack. When you are around something that triggers your symptoms, keep track of it. This can help you find a pattern in what triggers your symptoms. Record triggers on a piece of paper or in your asthma diary(What is a PDF document?).
2. Monitor your lung function. A trigger may not always cause symptoms. However, it can still narrow your bronchial tubes, making your lungs work harder. To identify triggers that do not always cause immediate symptoms, measure your peak expiratory flow (PEF) throughout the day. PEF will drop when your bronchial tubes narrow, so your PEF will drop when you are near things that trigger symptoms. Measure your PEF when you are around the common irritants mentioned in the "What are asthma triggers?" section to see if they are triggers. Record your PEF in your asthma diary.
3. Be tested for allergies. Skin or blood testing may be used to diagnose allergies to certain substances. Skin testing involves pricking the skin on your back or arms with one or more small doses of specific allergens. The amount of swelling and redness at the sites where your skin was pricked are measured to identify allergens to which you react. If your PEF drops when you are near an allergen, consider being tested for this allergen.
4. Share your trigger record with your health professional. After you have found some things that may trigger your asthma, you and your health professional can devise a plan for how to deal with them.

Now that you have read this information, you are ready to start identifying your asthma triggers. Let your health professional know of any triggers you identify.

If you have questions about this information, take it with you when you visit your health professional.

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