Asthma: risk factors
Asthma often begins in childhood, but may also appear during adolescence or during adult years. Environmental triggers in a susceptible person are the primary risk factors for asthma attacks. There is a wide range of such triggers, which include exposure to house dust mites, pollen, animals, specific foods, viral infections, moulds, fungi and environmental tobacco smoke. Avoidance of these triggers may help to control asthma.
Genetic factors are likely to contribute to the hypersensitive state of the airways of asthma sufferers. A number of other factors have been explored as potential explanations of changes in the risk of asthma, including exposure to infections in early life, indoor and outdoor pollution, environmental tobacco smoke, diet and drug use, obesity, rates of caesarean sections and breast feeding. The hygiene hypothesis suggests that lower levels of exposure to childhood infections increases the risk of asthma. However none of these explanations fully explain the rise in prevalence of asthma that has been seen in some countries.