If you have asthma, you may find that your symptoms are affected by the seasons. When the temperature dips, going outside can make breathing more of a chore. And exercising in the cold can bring on symptoms such as coughing and wheezing even faster.

Here’s a look at what causes cold-induced asthma and how to prevent attacks during the winter months.

When you have asthma, your airways (bronchial tubes) swell up and become inflamed in response to certain triggers. Swollen airways are narrower and can’t take in as much air. That’s why people with asthma often have trouble catching their breath.

Winter is an especially hard time for people with asthma. A Chinese study from 2014 found that hospital admissions for asthma increased during the winter months. And in the cold climate of the north of Finland, up to 82 percent of people with asthma experienced shortness of breath when they exercised in cold weather.

When you work out, your body needs more oxygen, so your breathing speeds up. Often, you breathe through your mouth to take in more air. While your nose has blood vessels that warm and humidify the air before it reaches your lungs, air that travels directly through your mouth remains cold and dry.

Exercising outdoors in cold weather delivers cold air rapidly to your airways. It also appears to increase your likelihood of having an asthma attack. What is it about the cold air that triggers asthma symptoms?

Cold air is hard on asthma symptoms for several reasons.

Cold air is dry

Your airways are lined with a thin layer of fluid. When you breathe in dry air, that fluid evaporates faster than it can be replaced. Dry airways become irritated and swollen, which worsens asthma symptoms.

Cold air also causes your airways to produce a substance called histamine, which is the same chemical your body makes during an allergy attack. Histamine triggers wheezing and other asthma symptoms.

Cold increases mucus

Your airways are also lined with a layer of protective mucus, which helps remove unhealthy particles. In cold weather, your body produces more mucus, but it’s thicker and stickier than normal. The extra mucus makes you more likely to catch a cold or other infection.

You’re more likely to get sick or be indoors when it’s cold

Colds, flu, and other respiratory infections tend to circulate during the winter months. These infections are also known to set off asthma symptoms.

Cold air can also drive you indoors, where dust, mold, and pet dander flourish. These allergens trigger asthma symptoms in some people.

Make sure your asthma is under control before winter arrives. See your doctor to develop an asthma action plan and then take the medicines your doctor prescribes. You may take medicine every day (for long-term control) or just when you need it (for quick relief).

Long-term controller medicines are drugs you take every day to manage your asthma symptoms. They include:

  • inhaled corticosteroids, such as fluticasone (Flovent Diskus, Flovent HFA)
  • long-acting beta-agonists, such as salmeterol (Serevent Diskus)
  • leukotriene modifiers, such as montelukast (Singulair)

Note: Long-acting beta-agonists are always used alongside inhaled corticosteroids.

Quick-relief medicines are drugs that you only take when you need them, such as before exercising in the cold. Short-acting bronchodilators and anticholinergics are examples of these drugs.

To prevent asthma attacks, try to stay indoors when the temperature dips very low, especially if it’s below 10°F (-12.2°C).

If you do have to go outside, cover your nose and mouth with a scarf to warm the air before you breathe it in.

Here are a few other tips:

  • Drink extra fluids in the winter. This can keep the mucus in your lungs thinner and therefore easier for your body to remove.
  • Try to avoid anyone who appears to be sick.
  • Get your flu vaccine early in the fall.
  • Vacuum and dust your home often to remove indoor allergens.
  • Wash your sheets and blankets every week in hot water to get rid of dust mites.

Here are some ways to prevent asthma attacks when you exercise outdoors in cold weather:

  • Use your inhaler 15 to 30 minutes before you exercise. This opens up your airways so you can breathe easier.
  • Carry an inhaler with you in case you have an asthma attack.
  • Warm up for at least 10 to 15 minutes before you work out.
  • Wear a mask or scarf over your face to warm the air you breathe in.

Cold is just one of many asthma triggers. Other things that can set off your symptoms include:

You know you’re having an asthma attack because of symptoms such as:

If you start to wheeze or feel short of breath, refer to the asthma action plan you wrote up with your doctor.

If your symptoms are so severe that you can’t speak, take your quick-acting medicine and seek immediate medical attention. You may need to stay under observation until your breathing stabilizes.

Here are some other general guidelines for what to do if you have an asthma attack:

  • Take two to six puffs from a quick-acting rescue inhaler. The medicine should open up your airways and help you breathe easier.
  • You may also be able to use a nebulizer instead of an inhaler. A nebulizer is a machine that turns your medicine into a fine mist that you breathe in.
  • If your symptoms aren’t severe but they don’t improve with the first few puffs from your inhaler, wait 20 minutes and then take another dose.
  • Once you feel better, call your doctor. You may need to keep taking your quick-acting medicine every few hours for a day or two.

Your asthma attack should subside once you’ve come in out of the cold and taken your medicine.

If your symptoms don’t improve or they seem to get worse whenever you’re out in the cold, you may need to see your doctor to review your asthma action plan. They may recommend changing medicines or coming up with other strategies for managing your condition.