The definition of nonallergic
asthma includes that subset of subjects with
asthma and with whom allergic sensitization cannot be demonstrated. These individuals should have negative skin prick test or in vitro specific-
IgE test to a panel of seasonal and perennial
allergens. Nonallergic
asthma occurs in 10% to 33% of individuals with
asthma and has a later onset than allergic
asthma, with a female predominance. Nonallergic
asthma appears to be more severe than allergic
asthma in many cases and may be less responsive to standard
therapy. Although many of the immunopathologic features of nonallergic
asthma are similar to those observed with allergic
asthma, some differences have been described, including a higher expression of
RANTES in mucosa and bronchoalveolar lavage fluid, as well as a higher
GM-CSF receptor alpha expression. Unbiased statistical methods, such as cluster analysis and latent class analysis, indicate that the lack of atopy is not the most important defining factor in assigning an individual to many specific phenotypes but rather is more important in some phenotypes than others, and appears to modulate the clinical expression of the disease. Despite an appreciation of this clinical entity for many years, many of its clinical implications remain unclear.