What is the Connection Between Humidity and Asthma?
Weather, any time of the year, is not a friend to people with asthma. But hot, humid days can be some of the most challenging weather conditions we have to contend with.
Have you noticed that your breathing gets worse on days when the humidity rises over 50%? If so, you're not alone.
I know that during the 30 years I lived in southern New Jersey, my asthma was definitely a lot worse than it's been in the 3 years I've lived in southwestern Colorado. New Jersey, right on the Atlantic coast, has much higher humidity levels than the high desert and mountains of my current home. I especially felt the effects of heat and humidity during the summer allergy season.
Understanding humidity and asthma
In the simplest terms, humidity is the amount of water or moisture in the air. When the media talks about humidity levels, they're referring to what is known as "relative humidity."1 This is the percentage of water in the air, compared to the maximum amount of water the air can actually hold at the current temperature. Hot air can hold more moisture than cold air. So, a relative humidity level of 70% on a hot day is going to feel a lot "wetter" than the same humidity level on a cold day.
According to the National Weather Service, humidity during hot summer months of less than 55 percent is "comfortable." Fifty-five to 65 percent humidity begins to feel "sticky," and anything over 65% is "oppressive."2 You can expect that humidity becomes an irritant type trigger for many asthmatics at levels of 65% and higher.
How humidity affects asthma
There are a few ways in which heat and humidity can affect breathing in people with asthma:3,4
- Hot, humid air is harder to breathe in. Moist air feels heavier and denser. Hot outdoor temperatures seem to magnify this effect.
- Humidity can activate sensory nerve fibers in the airways. These C-fibers are thought to narrow the airways and stimulate coughing.
- Hot, humid conditions provide the perfect breeding ground for asthma allergens. Dust mites, mold, and pollen are all common triggers for people with allergic asthma. Those allergens love hot, humid conditions.
- Heat and humidity raise ozone levels. Ozone is the culprit in air pollution. Humidity makes the air stagnant, trapping pollutants such as car exhaust, as well as pollen and mold spores.
In addition, extreme changes in temperature can be a trigger when you have asthma. Think about what a shock it can be when you walk out of a cold, air-conditioned building into suffocating outdoor heat.
Hot, humid indoor air can also make it harder to breathe.
Actions you can take to maintain asthma control
People with asthma are more likely to have asthma flare-ups, or exacerbations, during hot, humid conditions. In fact, a study done by researchers at the Children's Hospital of Michigan found that with as little as a 10% rise in humidity, there was an increase in hospital visits for asthma. The same held true for every 10-degree rise in atmospheric temperature.5 (They determined this by examining more than 25,000 hospital emergency department records.)
So, if you're living in hot, humid weather conditions, it's important to be vigilant about your asthma control.
How to protect your asthma from humidity
First of all, every person with asthma, whether child or adult, should have a written asthma action plan that will guide you in maintaining your asthma control. As soon as you notice any symptoms starting or worsening, refer to your action plan. But beyond that, here are a couple of other suggestions.
Check the air quality daily before going outdoors
Find out what the outdoor temperatures and relative humidity are. Check the local pollen and mold levels. When any of those factors are high, your best bet is to stay indoors in air conditioning as much as possible. Exercise indoors or at times of day when temps and humidity are lower.
Use your asthma medications
Be sure to take your controller medicine daily or twice daily as prescribed. Also, always keep your quick-relief/rescue inhaler on hand wherever you go, should symptoms crop up.
How have hot, humid summer weather conditions affected your asthma? Let us know in the comments or share your story here.
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