Evidence to support the alleged health benefits of air purifiers is mixed. For example, some research suggests that these machines may help decrease levels of airborne allergens, such as pet dander and dust, in a home. While some studies have found mild improvement of symptoms in people with allergies or asthma who use air purifiers, the machines aren’t a first-line treatment for these conditions. Instead, you’re better off preventing indoor air pollution in the first place by keeping your home clean and free of allergens and other particulate matter. If you think a HEPA filter or other type of air purifier might benefit you, be sure to do your research before making a purchase. Check rankings and reviews of air purifiers, such as those available from Consumer Reports. Your physician can give you more suggestions for managing allergies or asthma effectively.