Identifying asthma triggers forms the basis of environmental secondary prevention. These triggers may be allergenic or nonallergenic. Allergenic triggers include indoor allergens, such as house dust mites (HDMs), moulds, pets, cockroaches, and rodents, and outdoor allergens, such as pollens and moulds. Clinical observations provide support for the role of HDM exposure as a trigger, although avoidance studies provide conflicting results. Moulds and their metabolic products are now considered to be triggers of asthma attacks. Pets, dogs, and especially cats can undoubtedly trigger asthmatic symptoms in sensitised subjects. Avoidance is difficult and rarely adhered to by families. Cockroach allergens contribute to asthma morbidity, and avoidance strategies can lead to clinical benefit. Mouse allergens are mostly found in inner-city dwellings, but their implication in asthma morbidity is debated. In the outdoors, pollens can induce seasonal asthma in sensitised individuals. Avoidance relies on preventing pollens from getting into the house and on minimising seasonal outdoor exposure. Outdoor moulds may lead to severe asthma exacerbations. Nonallergenic triggers include viral infections, active and passive smoking, meteorological changes, occupational exposures, and other triggers that are less commonly involved. Viral infection is the main asthma trigger in children. Active smoking is associated with higher asthma morbidity, and smoking cessation interventions should be personalised. Passive smoking is also a risk factor for asthma exacerbation. The implementation of public smoking bans has led to a reduction in the hospitalisation of asthmatic children. Air pollution levels have been linked with asthmatic symptoms, a decrease in lung function, and increased emergency room visits and hospitalisations. Since avoidance is not easy to achieve, clean air policies remain the most effective strategy. Indoor air is also affected by air pollutants, such as cigarette smoke and volatile organic compounds generated by building and cleaning materials. Occupational exposures include work-exacerbated asthma and work-related asthma.
Authors: Gautier C, Charpin D. ;Full Source: Journal of Asthma & Allergy. 2017 Mar 7; 10:47-56. doi: 10.2147/JAA.S121276. eCollection 2017. ;