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Choice of Air Filtration Devices

By Aaaai.org

Question

I'm an internist in practice in Baltimore. I would like your opinion on home air purifiers--which of the many are allergist recommending and why. Are combination purifiers/humidifiers of any value?

Answer

I have enclosed below a review I wrote for the Current Literature section of this AADMC website. The article reviewed was written recently by Dr. Robert Wood of Johns Hopkins, an expert in environmental control measures. To obtain more information, I suggest that you read the entire article containing Dr. Wood's thoughtful discussion of the subject. The journal article can likely be obtained through your hospital library.

Air filtration devices in the control of indoor allergens

Summary
There continues to be great interest and aggressive advertising of air filtration device (AFD) aiming to help in the control of indoor allergens. This subject was reviewed by Wood of the Johns Hopkins Medical Institutions in Baltimore, MD. He pointed out that there is very limited definitive evidence to support the use of AFD in indoor allergen control. A variety of AFD have been marketed, mainly 1) electrostatic recipitators or 2) high efficiency particulate air (HEPA) types. Individual room units of adequate size tend to be more effective in that room than units placed centrally in the forced air system because the individual room units filter air more extensively in the room involved (assuming doors and window are kept closed).

Most of the controlled studies have dealt with room-sized units. HEPA/AFD can be very effective in reducing airborne levels of animal allergens, especially when carpeting is removed or cleaned thoroughly and frequently (see below). In contrast, any AFD has much less effect reducing airborne levels of dust mite or cockroach allergens. Dust mite and cockroach allergens are carried on larger particles that do not remain airborne for any length of time and are therefore less likely to be trapped by AFD. The concomitant frequent use of HEPA filter-equipped vacuum cleaners further reduces airborne animal allergen levels considerably.

The limited studies of the effects of AFD use in the home containing pets on asthma symptoms in individuals allergic to those animals have shown modest if any benefit of HEPA/AFD compared to placebo filtration. However, in one study there was a modest increase in PEFR and decrease in bronchial reactivity after 3 months use of the HEPA/ AFD. The author of this review concluded that the role of AFD on the control of indoor allergens is not defined. If benefit is seen, it is mainly related to reduction in the levels of animal allergens but this is not a true alternative to removal of the pet from the home if the patient is very allergic to those animals. Additional controlled studies, including assessment of effects of AFD on indoor mold levels, are needed.

Editor’s Comments
This thoughtful discussion by an expert in indoor environmental allergen control helps emphasize how little is known about the clinical effects of AFD in respiratory allergies. Yet, there has been extensive marketing and resultant use of these AFD by patients/families anxious to avoid the rigorous measures such as removal of all floor covering, impermeable covering of the mattress, appropriate washing of bedding and pet removal from the home. The recent findings that cat allergens can be transferred from such homes on the clothing of school children to the classroom environment raises the potential that very cat allergic classmates may be affected by contact with such "cat allergen carriers." Theoretically, one would expect that the use of a HEPA-equipped vacuum cleaner would be very helpful in reducing surface levels of allergens (dust mite and cockroach as well as animal) from floor covering and soft covered couches and chairs. Some of these vacuum cleaners have been shown to be reasonably effective, provided that there is a tight sealing of the airflow through the vacuum cleaner unit (not always the case). However, it is not yet clear whether use of such vacuum cleaners is an adequate substitute for removal of floor covering and over-stuffed furniture from the room.

This article has been syndicated from: http://www.aaaai.org/
Author: Aaaai.org

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