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CMAJ • November 30, 1999; 161 (90111)
© 1999 Canadian Medical Association or its licensors

Avoidance of environmental allergens

Increased exposure to environmental allergens likely contributes to the increased prevalence and severity of asthma. Therefore, avoidance of environmental allergens is one of the primary goals of asthma management.1,2 The association of IgE-mediated hypersensitivity to environmental allergens in asthma is well established; 60%-80% of both adults and children with asthma show hypersensitivity to environmental allergens, based on positive-immediate reaction to skin tests.3-6 The production of specific IgE antibodies against environmental allergens is a strong risk factor for acute asthma and a significant risk factor for severe asthma exacerbations on exposure to high concentrations of allergen.7-11 Severity of chronic asthma and airway hyperresponsiveness has also been correlated with degree of sensitivity to indoor allergens.3,12-14

Symptoms of asthma and objective measurements of airflow obstruction as well as airway hyperresponsiveness improve when patients avoid the environmental allergens to which they are allergic (Table 1).15-21 This has been demonstrated most dramatically when sensitized patients with asthma have been moved to allergy-free mountain institutions.21,22 When a cat is removed from a home, allergen concentrations decrease steadily over 6 months by 100- to 1000-fold.23 Using impervious mattress, pillow and comforter cases and washing bedding weekly in hot water reduces mite allergen by 100- to 1000-fold within a month.24 In a cockroach-infested urban dormitory, extermination followed by routine cleaning reduced cockroach allergen levels on the floor by 86%.25 These and many other studies support the efficacy of measures to minimize indoor allergens in the management of people with asthma with demonstrated sensitivity to these allergens.


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  		Table 1: Measures to minimize environmental factors contributing to asthma

 

Adherence to measures of allergen avoidance remains problematic. Without formal education programs, almost no one installs mattress covers.26,27 Adherence can be increased to 27% with repetitive clinic-based education and to 39% with the use of a computer-based educational program.26 Removal of a favourite pet becomes even more difficult. Patients' compliance with avoidance measures is much lower than that with medications, primarily because of the relatively quicker clinical improvement after medications compared with avoidance measures. The importance of educating patients to the crucial role of minimizing allergen exposure cannot be overemphasized.

Suggestions for future research

Recommendations

References

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  2. National Asthma Education and Prevention Program. Expert panel report: guidelines for the diagnosis and management of asthma. Washington: Department of Health and Human Services; 1991. NIH publ 91-3042.
  3. Peat JK, Britton WJ, Salome CM, Woolcock AJ. Bronchial hyperresponsiveness in two popoulations of Australian school children. III. Effect of exposure to environmental allergens. Clin Allergy 1987;17:291-30.[Medline]
  4. Burrows B, Martinez FD, Halonen M, Barbee RA, Kline. Association of asthma with serum IgE levels and skin test reactivity to allergens. N Engl J Med 1989;320:271-7.[Abstract]
  5. Bryant DH, Burns MW. Skin-prick test reactions to inhalant allergens in asthmatic patients. Med J Austral 1976;1:918-24.
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  10. Nelson RP Jr, DiNocolo R, Fernandez-Caldas E, Seleznick MJ, Lockey RF, Good RF. Allergen-specific IgE levels and mite allergen exposure in childhood with acute asthma first seen in an emergency department and in non-asthmatic control subjects. J Allergy Clin Immunol 1996;98:258-63.[Medline]
  11. O'Hallaren MT, Yunginger JW, Offord KP, Somers MJ, O'Connell EJ, Ballard DJ, et al. Exposure to an aeroallergen as a possible precipitating factor in respiratory arrest in young patients with asthma. N Engl J Med 1991;324:359-63.[Abstract]
  12. Sporik R, Holgate ST, Platts-Mills TAE, Cogswell J. House dust mite allergen (Der p1) exposure and the development of sensitization and asthma: a prospective study. N Engl J Med 1990;323:502-7.[Abstract]
  13. Turner KJ, Dowse GK, Stewart GA. Studies on bronchial hyperreactivity, allergic responsiveness and asthma in rural and urban children in the highlands of Papua, New Guinea. J Allergy Clin Immunol 1986;67:558-66.
  14. Dowse GK, Turner KJ, Stewart GA, Alpers MP, Woolcock AJ. The association between Dermatophagoides mites and the increasing prevalence of asthma in village communities within the Papua New Guinea highlands. J Allergy Clin Immunol 1985;75:75-83.[Medline]
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  19. Dietemann A, Bessor JC, Hoyet C, Orr M, Veror A, Pauli G. A double-blind, placebo-controlled trial of solididified benzoate applied in dwellings of asthmatic patients sensitive to mites: clinical efficacy and effect on mite allergens. J Allergy Clin Immunol 1993;91:738-46.[Medline]
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  22. Peroni DG, Boner AL, Vallone G, Antonelli I, Warner JO. Effective allergen avoidance at high altitude reduced allergen-induced bronchial hyperresponsiveness. Am J Respir Crit Care Med 1994;149:1442-6.[Abstract]
  23. Wood RA, Chapman MD, Adkinson NF Jr, Eggleston PA. The effect of cat removal on allergen content household dust samples. J Allergy Clin Immunol 1989;83:730-4.[Medline]
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  25. Surpong SB, Wood RA, Eggleston PA. Short-term effects of extermination and cleaning on cockroach allergen Bla g2 in settled dust. Ann Allergy 1996;76:257-9.
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  27. Corsage J. Preventive measures in house-dust allergy. Am Rev Respir Dis 1982;125:80-4.[Medline]




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