Air Filters, Air Cleaners and Allergies

How the Use of Air Filters and Air Cleaners Can Help Allergies

Woman Sneezing and Blowing Nose With White Tissue.
Air filters for allergies.. ballyscanlon / Getty Images

Indoor allergens, such as pet dander, dust mites, and indoor mold are a major cause of allergy and asthma symptoms. People suffering from indoor allergies are typically exposed to these common indoor contaminants for long periods of time -- particularly at night when sleeping. When allergy testing shows the presence of allergies to indoor allergens, avoidance techniques are often tried first to reduce allergy symptoms from developing.

This step may include using an air filter inside the home to reduce the amount of indoor airborne allergens that may cause or worsen allergy and asthma symptoms.

Allergens that Can Be Filtered From the Indoor Air

Generally speaking, when I talk to my patients about indoor allergens to be filtered from the air, I mean only allergens that come from indoor sources (such as pets and indoor mold contamination). I don’t talk about filtering outdoor allergens, such as pollens, from the indoor air. The best way to prevent pollen from coming indoors is to close windows and doors. If a small amount of pollen enters the home when windows or doors are briefly opened, most pollen is large enough to settle to the floor, where an air filter can’t catch it.

However, pet dander and common indoor molds are typically airborne -- and therefore able to be filtered using an air filter. Allergens that are typically too big to hang in the air (and thus get captured by an air filter) include dust mite and cockroach allergens, pollens and outdoor molds.

Air Filters in Heating, Ventilation and Air-Conditioning Systems

All heating, ventilation and air conditioning (HVAC) systems utilize some form of air filter in order to remove the amount of particulates from the air delivered by the system. Some HVAC units have the filter on the unit itself, others have the filter somewhere along the duct system, such as in the ceiling vents.

While many people forget to change the HVAC filters in their home regularly, these filters can be an effective tool against the fight against indoor allergens.

HVAC filters are rated according to their efficiency of filtering different sizes of airborne particles. This system, which is based on the "minimum efficiency reporting value" (MERV), rates household filters from MERV 1 to MERV 12. The higher the rating, the better the filter is at removing small particles.

The most inexpensive HVAC filters, made of blue woven fiberglass or other material, have a MERV 1 or 2 rating, and aren’t very good at filtering allergens from the air. The pleated fabric HVAC filters, made of fiberglass or cotton, do a much better job at filtering allergens, and have a MERV 11 or 12 rating. These filters are often sold as being effective at reducing airborne allergens within the home. HVAC filters should be changed every few months, or per the manufacturer’s recommendations, in order to keep them working properly.

Portable Room Air Cleaners

When an HVAC filter is not enough (normally when indoor pet or mold contamination is present) , a portable air cleaner should be considered. Air cleaners are usually of two types: Ionizer types and HEPA air filters.

I don't recommend purchasing an ionizer-based air cleaner. These products use an electrically charged metal plate to attract airborne particles like a magnet – which often does a good job of filtering the air, but creates ozone as a by-product. Ozone, a pollutant and irritant, has been shown to worsen asthma symptoms.

HEPA filters, or high-efficiency particulate air filters, use a disposable filter to clean the air. ​A HEPA-based filter will move room air from an intake vent, pass it the air through the filter, which, in turn, catches very small allergens, and then blows the clean, filtered air out an exhaust port. This is the best system for a portable air cleaner, in my opinion, and doesn’t generate hazardous ozone as a by-product. The actual filter needs to be changed routinely per manufacturer’s recommendations, however.


Sublett JL, Seltzer J, Burkhead R, et al. Air Filters and Air Cleaners: Rostrum by the American Academy of Allergy, Asthma and Immunology Indoor Allergen Committee. J Allergy Clin Immunol. 2010;125:32-8. 

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