What does "trigger" refer to?
The term "trigger" refers to something that contributes to an asthma attack in a person who already has asthma.
What are the principal indoor factors that affect asthma?
While there is no clear consensus about what causes asthma to develop in the first place, there is general agreement that certain triggers contribute to asthma stacks. Sometimes this is called exacerbation of asthma.
In the indoor environment, the following are generally recognized to be triggers of asthma attacks (1):
Environmental tobacco smoke (second-hand smoke) -- especially in young children (2)
Allergens produced by dust mites (2, 3)
Molds, fungus, dampness (4)
Allergens produced by cockroaches (5) (6)
Allergens produced by household pets, especially cats (7)
Nitrogen dioxide (NO2)
Not all asthmatics respond to all of these triggers.
What can be done to reduce the impact of these factors on children with asthma?
Many or all of these factors can be reduced or controlled, and this can improve the experience of people with asthma by reducing the frequency of attacks and/or need for medication or medical assistance (8, 9).
Home, school, and day care environments are all relevant targets for intervention efforts to reduce indoor factors.
The strategies that would be effective vary.
For environmental tobacco smoke, changes in individual behavior will obviously reduce the trigger in the home. Such changes are difficult to achieve.
For factors related to dampness, including molds and fungus, as well as cockroaches, repair or alternations to buildings may be needed to prevent the intrusion of water or insects, to improve ventilation, or to remove contaminated materials. These changes can require financial resources that may be beyond the means of many families, particularly low income families most likely to live in poor quality housing (10). Those most likely to be most in need of building alterations are least likely to be able to afford to pay for them or to need assistance in compelling landlords to do so. Participation by housing authorities and availability of funding to provide for repairs may be needed to solve these building factors.
Nitrogen dioxide usually originates indoors from poorly vented cooking or heating. Combustion fumes are associated with exacerbation of asthma (11). Reducing these exposures can require installation of ventilation to reduce indoor concentrations, which can cause a variety of health effects in addition to asthma.
Dust mites and pet allergens can be controlled through household practices including removal of materials that harbor the allergens, regular cleaning and washing of bedding materials, and covering mattresses and pillows in mite-proof covers (12, 13). Bare floors rather than carpets are recommended, though even this practice does not eliminate high dust mite levels in all cases (14). Reduction of humidity can reduce levels of dust mite allergen (15). Education of families can contribute to these practices.
To address indoor factors effectively requires participation of several sectors: health, housing, education, and environment (16).
Schools and day care facilities can also take steps to reduce triggers in their buildings.
1. Institute of Medicine. Clearing the Air: Asthma and Indoor Air Exposures. Washington, DC: National Academy Press, 2000.
2. Gold DR. Environmental tobacco smoke, indoor allergens, and childhood asthma. Environmental Health Perspectives 2000; 108 Suppl 4:643-51.
3. Sporik R, Platts-Mills TA, Cogswell JJ. Exposure to house dust mite allergen of children admitted to hospital with asthma. Clinical and Experimental Allergy 1993; 23:740-6.
4. Nicolai T, Illi S, von Mutius E. Effect of dampness at home in childhood on bronchial hyperreactivity in adolescence. Thorax 1998; 53:1035-40.
5. Potera C. Working the bugs out of asthma. Environmental Health Perspectives 1997; 105:1192-4.
6. Rosenstreich DL, Eggleston P, Kattan M, Baker D, Slavin RG, Gergen P, Mitchell H, McNiff-Mortimer K, Lynn H, Ownby D, Malveaux F. The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. New England Journal of Medicine 1997; 336:1356-63.
7. Nelson HS, Szefler SJ, Jacobs J, Huss K, Shapiro G, Sternberg AL. The relationships among environmental allergen sensitization, allergen exposure, pulmonary function, and bronchial hyperresponsiveness in the Childhood Asthma Management Program. Journal of Allergy and Clinical Immunology 1999; 104:775-85.
8. Shapiro GG, Wighton TG, Chinn T, Zuckrman J, Eliassen AH, Picciano JF, Platts-Mills TA. House dust mite avoidance for children with asthma in homes of low-income families. Journal of Allergy and Clinical Immunology 1999; 103:1069-74.
9. Carswell F, Oliver J, Weeks J. Do mite avoidance measures affect mite and cat airborne allergens? Clinical and Experimental Allergy 1999; 29:193-200.
10. Kuster PA. Reducing risk of house dust mite and cockroach allergen exposure in inner-city children with asthma. Pediatric Nursing 1996; 22:297-303.
11. Ostro BD, Lipsett MJ, Mann JK, Wiener MB, Selner J. Indoor air pollution and asthma. Results from a panel study. American Journal of Respiratory and Critical Care Medicine 1994; 149:1400-6.
12. Vanlaar CH, Peat JK, Marks GB, Rimmer J, Tovey ER. Domestic control of house dust mite allergen in children's beds. Journal of Allergy and Clinical Immunology 2000; 105:1130-3.
13. Bahir A, Goldberg A, Mekori YA, Confino-Cohen R, Morag H, Rosen Y, Monakir D, Rigler S, Cohen AH, Horev Z, Noviski N, Mandelberg A. Continuous avoidance measures with or without acaricide in dust mite-allergic asthmatic children. Annals of Allergy, Asthma, and Immunology 1997; 78:506-12.
14. Chew GL, Burge HA, Dockery DW, Muilenberg ML, Weiss ST, Gold DR. Limitations of a home characteristics questionnaire as a predictor of indoor allergen levels. American Journal of Respiratory and Critical Care Medicine 1998; 157:1536-41.
15. Warner JA, Frederick JM, Bryant TN, Weich C, Raw GJ, Hunter C, Stephen FR, McIntyre DA, Warner JO. Mechanical ventilation and high-efficiency vacuum cleaning: A combined strategy of mite and mite allergen reduction in the control of mite-sensitive asthma. Journal of Allergy and Clinical Immunology 2000; 105:75-82.
16. Kattan M, Mitchell H, Eggleston P, Gergen P, Crain E, Redline S, Weiss K, Evans R, 3rd, Kaslow R, Kercsmar C, Leickly F, Malveaux F, Wedner HJ. Characteristics of inner-city children with asthma: the National Cooperative Inner-City Asthma Study. Pediatric Pulmonol 1997; 24:253-62.
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