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 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:
- 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.
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:
- 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.
In some cases, people can prevent humidity-related asthma symptoms from developing by:
Checking the air quality
The air quality index (AQI) indicates the daily level of pollutants, such as smog. Air quality levels vary daily and between locations. The more pollutants in the air, the harder it can be for a person with asthma to breathe.
The AQI measures air quality on a scale from 0–500. The higher the number, the worse the air quality. Air quality tends to be worse on hot and humid days. Staying inside when the air quality is poor might prevent asthma symptoms developing.
Controling humidity indoors
Humidity does not only develop outdoors. Humidity levels can also rise inside. However, it is possible to control humidity levels indoors.
According to the Environmental Protection Agency (EPA), it is best to keep humidity levels between 30–50%.
Lower humidity decreases mold growth, dust mites, and cockroaches, all of which can trigger asthma symptoms.
Check indoor humidity levels with a humidistat, available at many hardware or home improvement stores, or online.
People can reduce indoor humidity by:
- opening windows in the bathroom while showering or bathing
- using a dehumidifier
- running an air conditioner
- fixing leaky pipes
Avoiding exercising outdoors when humidity levels are high
Exercising outdoors when the weather is warm and humid can lead to airway irritation. However, people can still exercise in a gym, pool, or somewhere else that has air conditioning.
There is no optimal weather condition for people with asthma, but many find that consistency in temperatures and conditions is better for symptoms.
Allergens and pollutants in the air are two of the most significant factors that affect asthma symptoms. Certain types of weather may increase both air pollution and common allergens.
Some people with asthma experience problems in very cold or hot temperatures, which can increase airway irritation. Mild temperatures and low levels of humidity might decrease the risk of airway irritation.
Not only is humidity a problem for people with asthma, but other weather conditions can also lead to symptoms.
The weather conditions most likely to trigger asthma include:
- Extreme heat: When temperatures climb, pollution levels may also rise, which can trigger asthma symptoms.
- Cold, dry air: Cold, dry air can irritate the airways and lead to bronchospasm. This often results in common asthma symptoms, including coughing, wheezing, and trouble breathing.
- Windy conditions: Common allergens, such as pollen, blow around in the wind. Add rain into the mix, and it can lead to an increase in mold spores. Both pollen and mold are common triggers for people with asthma.
- Rapid changes in temperature: Some people are also sensitive to a quick change in weather conditions, such as heat one day and cold the next.
Although everyone with asthma has different triggers, humidity and asthma symptoms go hand in hand for many people.
Increased moisture in the air, especially in high temperatures, can trigger bronchospasm and asthma symptoms. Other weather conditions, such as cold, dry air, can also lead to asthma flares.
Monitoring humidity and air quality are helpful to prevent humidity-related asthma symptoms from developing.