What Causes or Triggers Asthma?

People with asthma have inflamed airways which are sensitive to things which may not bother other people. These things are "triggers."

Asthma triggers vary from person to person. Some people react to only a few while others react to many.

If you have asthma, it is important to keep track of the causes or triggers that you know provoke your asthma. Because the symptoms do not always occur right after exposure, this may take a bit of detective work. Delayed asthma episodes may occur depending on the type of trigger and how sensitive a person is to it.

The most common asthma triggers include:

Allergies (Allergic Asthma)

Substances that cause allergies (allergens) can trigger asthma. If you inhale something you are allergic to, you may experience asthma symptoms. It is best to avoid or limit contact with known allergens to decrease or prevent asthma episodes.

Common allergens that cause allergic asthma include:

Learn more about Allergic Asthma.

Irritants in the Air

Irritants in the environment can also bring on an asthma episode. Although people are not allergic to these items, they can bother inflamed, sensitive airways:

Respiratory Illness

Respiratory infections are the most common asthma trigger in children.


Exercise and other activities that make you breathe harder can affect your asthma. Exercise—especially in cold air—is a frequent asthma trigger. Exercise-induced bronchoconstriction (EIB) is a form of asthma that is triggered by physical activity. It is also known as exercise-induced asthma (EIA). Symptoms may not appear until after several minutes of sustained exercise. (If symptoms appear sooner than this, it usually means you need to adjust your treatment.) With proper treatment, you do not need to limit your physical activity.

Learn more about Exercise-Induced Asthma.


Dry wind, cold air or sudden changes in weather can sometimes bring on an asthma episode.

Feeling and Expressing Strong Emotions

  • anger
  • fear
  • excitement
  • laughter
  • yelling
  • crying

When you feel strong emotions, your breathing changes – even if you don’t have asthma. It may cause wheezing or other asthma symptoms in someone with asthma.


Some medicines can also trigger asthma:

  • If you are sensitive to aspirin and NSAIDs (nonsteroidal anti-inflammatory drugs)
  • If you take medicines known as beta blockers – they can also make asthma harder to control

Other Asthma Triggers

Other triggers to consider and discuss with your healthcare provider are:

  • sulfites in food
  • hormonal changes during the menstrual cycle
  • other medical problems like reflux

Talk to your health care provider about your asthma and your triggers. Be sure to discuss any changes in your asthma management.

Medical Review September 2015.