Ozone air purifiers: Can they improve asthma symptoms?

My daughter has asthma and I'm wondering if she would benefit from an ozone air purifier in her room. What do you think?

- Ryan / Minnesota

Mayo Clinic asthma and allergy specialist James Li, M.D., and colleagues answer select questions from readers.

Answer

Despite manufacturer's claims, ozone air purifiers don't remove particles from the air that may trigger asthma attacks. In fact, inhaled ozone may even make asthma worse.

Ozone generators sold as air purifiers intentionally produce ozone, which is a toxic gas. Ozone is a molecule made of three atoms of oxygen. Two of these atoms form the basic oxygen molecule. The third atom can detach from the ozone molecule and reattach to molecules of other substances, changing their chemical composition. This is the basis of manufacturer claims that ozone "purifies" the air. But inhaling ozone — even in small amounts — can damage lung tissue. Inhaled ozone may cause throat irritation, coughing, chest pain and shortness of breath. It can increase the risk of developing a respiratory infection.

Some ozone air purifiers are made with an ion generator or "ionizer" in the same unit. You can also buy ionizers as separate units. Ionizers do take particles out of the air. Ions stick to particles, causing them to attach to nearby surfaces or to each other and settle out of the air. But ionizers don't work any better than high-efficiency particulate air (HEPA) filters or electrostatic filters in removing allergens from the air and may generate unwanted ozone.