Laura Dorwart is a health journalist with expertise in disability rights, mental health, and pregnancy-related conditions. She has written for publications like SELF, The New York Times, VICE, and The Guardian.

Daniel More, MD, is a board-certified allergist and clinical immunologist with a background in internal medicine.

Asthma is a chronic medical condition that tightens and inflames the airways in the lungs. More than 25 million Americans—including more than 5 million children—have asthma.  

Asthma symptoms include wheezing, coughing, excess mucus, and chest tightness. These symptoms, as well as asthma attacks (when symptoms worsen), can be triggered by allergens (normally harmless substances that trigger an allergic reaction) and other irritants.  

It's no wonder that air purifiers can be so enticing. These devices purportedly remove indoor pollutants like dust, allergens, bacteria, and mold from the air and replace them with clean air. Understandably, many people with asthma wonder if putting an air purifier in their home can help ease their symptoms. You may be one of them.

Learn more about whether air purifiers address asthma symptoms, if they make symptoms worse, and how to treat them.

An air purifier is a device that uses a filter and a fan to trap small particles from the air and recirculate the room with clean air. It can remove many pollutants that trigger allergy symptoms, such as:

There are many different types of air purifiers. High-efficiency particulate air (HEPA) filters are able to capture 99.7% of all particles 0.3 microns or smaller. HEPA filters can be sold on their own or used in other systems, such as your heating, ventilation, and air conditioning (HVAC) system or vacuum cleaner. 

Other types of air purifiers include:

While air purifiers clean indoor air, humidifiers add moisture to the air. If your asthma is triggered by dry air, a humidifier could potentially help you control your symptoms. However, humidifiers can promote mildew, bacteria, dust mites, and mold growth, which can make symptoms worse for some people with asthma.

The U.S. Food and Drug Administration (FDA) has not licensed any air purifiers as medical devices for the purpose of treating asthma. However, some research suggests that air cleaners can help control asthma symptoms by limiting exposure to common asthma triggers. Air purifiers might do this by:

Avoid air purifiers that generate ozone, a chemical that can harm your health even at low levels of exposure. The U.S. Environmental Protection Agency (EPA) warns against purchasing ozone-producing air cleaners, which are usually electrostatic air filters or ionizers.

Ozone is an unstable gas molecule and it is a lung irritant. It can cause breathing problems, shortness of breath, chest tightness, throat irritation, and coughing. It can make asthma symptoms worse and put you at a higher risk of developing a respiratory infection.

Also, remember that air purifiers can’t remove every asthma trigger, such as outdoor allergens, gases, fumes, or mold caused by moisture. It’s always best to treat your triggers “at the source,” if possible.

Stop outdoor air particles from becoming indoor air nuisances by:

If you're ready to buy an air purifier, keep a few pointers in mind:

Some guidelines for using an air purifier may help you control your asthma symptoms:

A whole-house HEPA filter should be sized to your home and installed by a professional HVAC company. The filter should be changed once every three months.

While an air purifier can help some people control their asthma symptoms, you can take other steps to stop asthma triggers in their tracks:

In addition to using an air purifier, you can take these steps to improve indoor air quality and reduce your exposure to irritants, pollutants, and allergens:

Air purifiers are supposed to remove pollutants, allergens, and irritants from the air and improve indoor air quality. There is some evidence that air purifiers can help people with asthma control their symptoms. If you wish to buy a purifier, consider the device's cost, size, efficiency, volume, certification, and effectiveness. Avoid ionizers and other air purifiers that produce ozone, which can irritate the lungs. 

To manage asthma symptoms and reduce exposure to allergens, you can also take measures like reducing moisture, keeping pet dander under control, vacuuming regularly, controlling pests, shutting doors and windows, and using allergen-free mattress covers.

The Allergy & Asthma Network cautions that "no air cleaner or filter can do it all." It recommends going to the source of the allergen, whether it’s mold, dust mites, pets, or insects. Air filtration is only one of several measures that may ease allergy and asthma symptoms in children and adults.

High-efficiency particulate air (HEPA) filters are the best air purifiers for asthma symptoms. They're designed to remove more than 99.7% of small particles from the air—or at least those that are 0.3 microns or smaller. These particles include dust mites, mold spores, pet dander, smoke, pollen, and many other common pollutants and irritants that trigger asthma symptoms.

There’s some evidence that air purifiers, which clean indoor air by removing small particles like pollutants and allergens, can help with asthma symptoms.

Humidifiers add moisture into the air. While humidifiers can help some people whose symptoms are triggered by dry air, they can also potentially make asthma symptoms worse by promoting mold growth.

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Rice JL, Brigham E, Dineen R, et al. The feasibility of an air purifier and secondhand smoke education intervention in homes of inner city pregnant women and infants living with a smoker. Environ Res. 2018;160:524-530. doi:10.1016/j.envres.2017.10.020.

Miyoshi T, Furuie W, Otani Y, et al. Can air purifier promote the indoor cleanliness and improve the patients with asthma? Eur. Respir. J. 2018;52:1691. doi:10.1183/13993003.congress-2018.PA1691.

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