How does humidity affect asthma?

Humidity is a measure of how much moisture there is in the air. Many people with asthma find that humid weather makes their symptoms worse.

People can prevent humidity-related asthma symptoms using a range of strategies, including taking medication, controlling indoor humidity levels, and avoiding exercising in humid conditions.

Keep reading to learn how humidity and the weather can affect asthma symptoms and what to do to prevent a flare. We also look at the best and worst weather conditions for asthma.

Humidity and asthma

Humidity refers to how much moisture or water vapor is in the air.

People may notice their asthma symptoms get worse on humid days when there is a lot of moisture in the air. This is especially true when exercising in humid conditions.

High levels of humidity may play a role in asthma symptoms in a variety of ways.

The increased moisture can directly irritate the airways, and humidity can increase the levels of other substances in the air that irritate the bronchial tubes, such as pollen and pollution.

High humidity can trigger asthma symptoms, including:

  • coughing
  • wheezing
  • chest tightness

Small-scale research has looked into how humid weather affects a person’s lungs. The researchers tested airway resistance — a measure of how easy it is to breathe — in six people with asthma and six people without.

After experiencing hot, humid air (49°C and 75–80% humidity) for 4 minutes, people with asthma had a 112% increase in airway resistance as opposed to the healthy group that only had a 22% increase in airway resistance.

Why does humidity affect asthma?

Humidity likely causes asthma symptoms because it triggers bronchoconstriction, which is a narrowing of the airways.

Bronchoconstriction may occur because hot, humid air activates C fibers, which are sensory nerve fibers in the airways. Stimulation of C fibers may narrow the airways and stimulate coughing, which makes it difficult to breathe.

High humidity levels create the perfect breeding ground for mold and dust mites, which often trigger asthma. Higher levels of humidity may also increase air pollution. For example, ozone, which is an air pollutant, rises when humidity levels increase.

Increased levels of humidity also often mean higher temperatures. The highest humidity levels usually occur during the summer months. The combination of heat and humidity can irritate the airways making breathing more difficult.

How to manage symptoms

While it is not possible to control the weather and humidity levels outdoors, people can manage humidity-related asthma symptoms by:

Staying indoors on humid days

Get the weather report from your local news station and check the humidity levels. When high humidity advisories are in effect, try to stay indoors as much as possible.

Recognizing signs of an asthma flare

Recognizing symptoms as soon as they start can prevent an asthma flare from becoming worse. Signs include:

  • coughing
  • wheezing
  • shortness of breath
  • chest tightness

When symptoms start, people should follow the asthma action treatment plan they developed with their doctor.

Taking fast-acting bronchodilators

Fast-acting bronchodilators relax the muscles in the airways, which opens them up. As the narrowing decreases, breathing becomes easier. Common fast-acting inhalers to treat asthma include albuterol and Xopenex.