What Causes Asthma? Common Triggers Explained

Medically Reviewed by Smitha Bhandari, MD on October 03, 2022
9 min read

No one really knows what causes asthma. What we do know is that asthma is a chronic inflammatory disease of the airways. The causes can vary from person to person. Still, one thing is consistent: When airways come into contact with a trigger, they become inflamed, narrow, and fill with mucus.

When you have an asthma attack, your airways narrow and it gets hard to breathe. This can result from spasms of the muscles around the airways, inflammation and swelling of the mucosal membrane that lines them, or high amounts of mucus inside them. You might have shortness of breath, wheeze or cough as your body tries to get rid of mucus.

Why do you have asthma and your friend doesn't? No one knows for sure. Allergies play a role for many people, as do genetics.

If you or a loved one has asthma, it's important to understand what your triggers are. Once you figure that out, you can take steps to avoid them. As a result, you’ll have fewer and less severe asthma attacks.

Some known triggers of asthma attacks include:

  • Allergies
  • Food and food additives
  • Exercise
  • Heartburn
  • Smoking
  • Sinusitis
  • Medications
  • Weather
  • Smoke

Allergies with asthma is a common problem. Eighty percent of people with asthma have allergies to things in the air, like tree, grass, and weed pollens; mold; animal dander; dust mites; and cockroach droppings. In one study, children with high levels of cockroach droppings in their homes were four times more likely to have childhood asthma than children with low levels. An allergy to dust mites is another common asthma trigger.

If you have asthma that’s hard to control, see an allergist to find out if you have allergies. Treating your allergies with medication and avoiding your triggers can help lower the odds of a severe asthma attack.

Food allergies can cause mild to severe life-threatening reactions. They rarely cause asthma without other symptoms. If you have food allergies, asthma can be part of a severe, life-threatening reaction called anaphylaxis. The most common foods associated with allergic symptoms are:

  • Eggs
  • Cow's milk
  • Peanuts
  • Tree nuts
  • Soy
  • Wheat
  • Fish
  • Shrimp and other shellfish
  • Salads
  • Fresh fruits

Food preservatives can trigger isolated asthma, especially sulfite additives, like sodium bisulfite, potassium bisulfite, sodium metabisulfite, potassium metabisulfite, and sodium sulfite, which are commonly used in food processing or preparation.

For about 80% of people with asthma, a heavy workout can cause airways to narrow. Exercise is often the main asthma trigger. If you have exercise-induced asthma, you will feel chest tightness, cough, and have trouble breathing within the first 5 to 15 minutes of an aerobic workout. For most people, these symptoms go away in the next 30 to 60 minutes of exercise. But up to 50% of people with exercise-induced asthma may have another attack 6 to 10 hours later. A slow warm-up may help prevent this.

If you have severe asthma and you’re not active now, talk to your doctor first about how to track your breathing and choose the right activities. When it’s winter, avoid exercising outdoors in very cold weather because the exposure could trigger asthma.

Severe heartburn and asthma often go hand-in-hand. Up to 89% of people with asthma also have severe heartburn (you might hear your doctor call it gastroesophageal reflux disease, or GERD). It usually happens at night when you're lying down. Normally, a valve prevents stomach acids from backing up into your esophagus (the tube food goes down when you eat). When you have GERD, this valve doesn't work like it should. Your stomach acids reflux, or back up, into the esophagus. If the acids reach your throat or airways, the irritation and inflammation they cause could trigger an asthma attack.

Clues that suggest reflux as the cause of asthma include the start of asthma in adulthood, no family history of asthma, no history of allergies or bronchitis, difficult-to-control asthma, or coughing while lying down.

If your doctor suspects this problem, they may recommend specific tests to look for it, change your foods, or offer medications.

People who smoke cigarettes are more likely to get asthma. If you smoke with asthma, it may make symptoms like coughing and wheezing worse. Women who smoke during pregnancy raise the risk of wheezing in their babies. Babies whose mothers smoked during pregnancy also have worse lung function. If you have asthma and you're a smoker, quitting is the most important step you can take to protect your lungs.

Much like asthma causes inflammation in the lining of your airways, sinusitis causes inflammation in the mucus membranes that line your sinuses. This makes the membranes put out more mucus. If you have asthma and your sinuses get inflamed, your airways may too. Prompt treatment of a sinus infection can relieve asthma symptoms.

Cold, flu, bronchitis, and sinus can cause an asthma attack. These respiratory infections that trigger asthma can be viral or bacterial. They're a common cause of asthma, especially in children under age 10. You may be more likely to have an attack for up to 2 months after an upper respiratory infection. Anywhere from 20% to 70% of adults with asthma also have sinus disease. Also, 15% to 56% of people with allergic rhinitis (hay fever) or sinusitis also have signs of asthma.

Many people with asthma are sensitive to certain medications that can trigger an asthma attack. If you have asthma, you need to be aware of what other medications may be triggers. You don’t need to avoid these medications unless you know that they’re triggers. But if they have never triggered your asthma, it is still best to take them with caution because a reaction can happen at any time.

Below is a list of the most common medications known to trigger asthma or related symptoms. However, if you are prescribed any medication that you think may be causing your asthma to get worse, discuss it with your doctor.

  • Aspirin and other painkillers. About 10% to 20% of people with asthma have sensitivity to aspirin or a group of pain relievers called nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen. These drugs are often used to treat pain and reduce fevers.
    Asthma attacks caused by any of these medications can be severe and even fatal, so people who have known aspirin-sensitive asthma should avoid them completely. Products with acetaminophen are generally considered safe for people who have asthma, but you should still talk with your doctor about whether to use them. For some people, there is a small possibility that acetaminophen may trigger an asthma attack.
    If you have an aspirin sensitivity, it is important that you read the labels of all over-the-counter medications used to treat pain, colds and coughs, and fever. Also, inform your doctor so that these medications are not prescribed for you. If you have any questions about whether a certain medication could trigger your asthma, seek advice from your doctor.
  • Beta-blockers. Beta-blockers are commonly prescribed medications used to treat heart conditions, high blood pressure, migraine headache, and, in eye drop form, glaucoma. Your doctor must determine the need for these medications, and you can take a few trial doses to see if they affect your asthma. It is important that you inform all of your health care providers that you have asthma. This includes even your eye doctor.
    Examples of beta-blockers are Corgard, Inderal, Normodyne, Pindolol, and Trandate.
  • ACE inhibitors. These are used to treat heart disease and high blood pressure. These medications can cause coughs in about 10% of the patients who use them. This cough is not necessarily asthma. But it can be confused with asthma or, in the case of unstable airways, can actually trigger wheeze and chest tightness. If you are prescribed an ACE inhibitor and develop a cough, speak with your doctor.
    Some ACE inhibitors are Accupril, Aceon, Altace, Captopril, Lotensin, Mavik, Monopril, Prinivil, Tarka, Univasc, Vasotec, and Zestril.

If you have severe asthma, talk to your doctor about any medication you’re considering taking, even if it’s an over-the-counter medication.  If you know that you're sensitive to particular drugs, make sure your doctor notes the problem on your chart. Always talk to your pharmacist about this reaction before you start a new medication.

Irritants. Tobacco smoke, smoke from wood-burning appliances or fireplaces, strong odors from perfumes, cleaning agents, etc., can all trigger asthma. So can air pollution, workplace dust, or fumes from chemicals.

Weather. Cold air, changes in temperature, and humidity can cause an attack.

Strong emotions. Stress and asthma are often seen together. Anxiety, crying, yelling, stress, anger, or laughing hard can bring on an asthma attack.

When you have asthma, your airways are always inflamed and sensitive. They react to a variety of external triggers. Contact with these triggers is what causes asthma symptoms. Your airways tighten and get more inflamed, mucus blocks them, and your symptoms get worse. An asthma attack can start right after exposure to a trigger or several days or even weeks later.

Reactions to asthma triggers are different for each person and vary from time to time. Something may bother you but not others with asthma. You might have many triggers while they have none. And while avoiding triggers is a good way to control asthma, the best way is to take medications and follow treatments exactly as prescribed by your doctor in your asthma action plan.

Figuring out what was going on around you when you had an attack is the first step to identifying your triggers.

Your doctor may also do blood testing or ask you to use a device called a peak flow meter. It measures how much air you exhale and how quickly it comes out. It can alert you to changes in your breathing and the onset of asthma symptoms.

Ask your asthma doctor if using a peak flow meter would help you narrow down the causes of your asthma.

It can be tough to identify them all, and they can change. For example, you might not have been bothered by tree pollen when you were a child, only to have a problem with it as an adult.

Even when you know your triggers, you might have a hard time avoiding them in certain situations. For example, you may notice that your workplace is cleaned with a cleaning product that bothers your lungs.

That’s why it’s so important to work closely with the doctor who treats your asthma. They can help you think of strategies to avoid triggers, or at least cut down on the amount of time you spend near them. They can also make sure you have the right medication when an asthma attack does strike.

Warning signs of a potential asthma attack include:

  • Needing more rescue inhaler medication (such as albuterol).
  • A cough that gets worse.
  • Feeling like you can’t breathe or like someone’s sitting on your chest.
  • Waking up at night feeling like you can’t breathe.
  • Not being able to be active or exercise without getting winded or wheezing.          

Use your asthma rescue inhaler medication as soon as you start to feel an attack come on. If it doesn’t seem to work and you feel like you still can’t breathe, call 911 so you can get to an emergency room right away.

If you have a steroid medicine at home (such as prednisone), you can take it on your way to the ER.