[Epidemiology of respiratory allergies: current data].

Respiratory allergic diseases include seasonal allergic rhinitis or hay fever, perennial allergic rhinitis and allergic asthma. Prevalence of asthma is difficult to assess through epidemiological questionnaires. In France hay fever roughly affects 6% of children and 18% of teenagers and nasal allergies, more than one fourth of young adults. Prevalence of asthma is equal to 10 to 15% in teenagers and 7 to 9% in young adults. Risk factors include genetic as well as environmental factors. The role of the former have been exemplified in family studies, especially twin studies, and surveys of inbred populations. Environmental factors can be allergic or non-allergic. The influence of allergenic exposure on sensitization, occurrence and severity of respiratory allergic disease is well documented. The triggering influence of non-allergenic factors on established allergic diseases is also clear. In contrast, their implication in allergic sensitization and occurrence of allergic diseases need to be clarified.