Rhinitis: a dose of epidemiological reality.

In the wide spectrum of medical practice, rhinitis is often incorrectly assumed to be solely allergic in etiology. Consequently, other rhinitis subtypes (nonallergic and mixed) remain under-diagnosed. This is of concern because inaccurate diagnosis may lead to unsatisfactory treatment outcome. Contributing to this under-diagnosis is the fact that primary care practitioners do not often have at their disposal the same diagnostic tools as the allergist. Tools that the allergist is more likely to use include nasal cytology, skin testing and in vitro assays for specific immunoglobulin E. Patients with pure nonallergic rhinitis have negative skin tests or clinically irrelevant positive results. Mixed rhinitis refers to the presence of both allergic and nonallergic rhinitis components within the same individual. Allergic rhinitis more commonly develops before the age of 20, whereas nonallergic rhinitis affects an older population and disproportionately more females. The type of nasal symptoms manifested by the patient usually does not differentiate allergic from nonallergic rhinitis. Vasomotor rhinitis is the most common form of nonallergic rhinitis, followed by nonallergic rhinitis with eosinophilia and others. In terms of estimated prevalence, allergic rhinitis affects approximately 58 million Americans, 19 million have pure nonallergic rhinitis and 26 million have mixed rhinitis. Thus a wide spectrum of relevant epidemiologic information can be used to assist in determining the differential diagnosis of rhinitis. Physicians are reminded to look further and consider whether a rhinitis patient truly has pure allergic rhinitis or whether a diagnosis of mixed rhinitis or nonallergic rhinitis is more appropriate.