Do Indoor Air Quality Control Measures Work?
March 1, 1998
Do Indoor Air Quality Control Measures Work?
ABSTRACTS & COMMENTARY
Synopsis: House dust mite avoidance measures resulted in improved symptoms and peak flow in a group of patients with allergy and asthma symptoms. Neither the use of Allerpet-C nor repeated cat washing resulted in consistent and sustained reduction of Fel d 1.
Sources: Cloosterman AS, et al. J Allergy Clin Immunol 1997;100:313-319; Avner DB, et al. J Allergy Clin Immunol 1997;100:307-312; Perzanowski MS, et al. J Allergy Clin Immunol 1997;100:428-430.
The advice we give to our allergic and asthmatic patients often appears logical to us, but it has not necessarily been substantiated by high-level evidence. Many recommended environmental control measures are difficult to carry out and disruptive of patients' lifestyles. If interventions are to be effective, physicians should be reasonably sure of their effect on clinical outcome. Three recent studies attempt to evaluate the effectiveness of strategies aimed at reducing house dust mite and cat allergen exposure. Cloosterman and colleagues from the Netherlands evaluated 29 patients with allergy and asthma symptoms but with normal pulmonary function. Approximately one-quarter were smokers, and no patient was on medication. Subjects were randomly allocated to either a house dust mite avoidance or placebo intervention. Avoidance measures included application of Acarosan to living room and bedroom floors and the use of impermeable covers for mattresses and bedding. Compared to placebo, significant improvements were noted in sleep disturbance, wheezing, and overall symptoms. Peak flow also demonstrated significant improvement over the six-week course of the study.
To evaluate the practice of cat washing, Avner and associates compared three different techniques, measuring airborne Fel d 1 immediately before and three hours after washing. Decreases in airborne allergen was noted after bathing at a veterinarian's office for five consecutive weeks (44%). Weekly immersion for three minutes in up to 30 L of water for four weeks resulted in a 79% reduction in allergen. Washing and rinsing led to an 84% reduction. Cat-to-cat variability in Fel d 1 load was reported, with concentrations of Fel d 1 per cat estimated by shaving ranging from three to 142 mg. However, repeated washing failed to sustain a decrease in measurable aero-allergen.
In the last study, Perzanowski and coworkers evaluated Allerpet-C, a commercially sold spray that has been purported to limit shedding of cat allergen. This material, which contains sterilized water, hydrolyzed animal protein, allantoin, aloe vera gel, imidazolidinyl urea, and collagen, was no more effective than wiping the cat with a wet cloth and was less effective than washing by five-fold.
COMMENT BY ALAN M. FEIN, MD
While many clinicians focus on pharmacologic management of asthma, it is clear that environmental allergens reduction is also a strategy worth evaluating. House dust mite allergy affects up to one-fifth of the young adult population, of which one-third of these have asthma. Concentrations of house dust mites and duration of exposure have been linked to the risk of overt asthma. Cat allergy is also common and may persist even when the animal has been removed for weeks. In addition, significant numbers of individuals with cat sensitivity live with these animals, despite medical recommendations to the contrary.
Do allergen avoidance techniques work, and do they improve outcomes and quality of life? Clearly, not all approaches are as effective as others. Measures aimed at reducing house dust mites are effective in patients with mild asthma at least over the short term of the study (6 weeks). Patients not only had mildly better peak flow but reported improved nocturnal and daytime symptoms, as well as an improvement in wheezing. While improvements in the active intervention group were modest, they were consistent and measurable.
Cat allergy is a particularly vexing problem, because it appears to be so easily solvable. Unfortunately, many patients refuse to remove the cat from the home and are unwilling to go through desensitization. Washing cats or using commercial agents to reduce shedding is often advised. The two studies reported do not provide consistent information upon which to recommend these practices. While various washing programs seemed initially effective, reduction in Fel d 1 was not sustained at six weeks. Likewise, the use of the product Allerpet-C was no more effective than wiping the cat with a wet cloth.
Currently, house dust mite suppression appears to work. For the more vexing problem of what to do with the cat-sensitive patient, removal seems to be the only option that is likely to be beneficial. (Dr. Fein is Director, Center for Pulmonary and Critical Care, Northshore University Hospital, Manhasset, NY.)
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