Asthma and chemical hypersensitivity: prevalence, etiology, and age of onset.

This study investigates asthma's national prevalence and potential overlap with chemical hypersensitivity. It also examines asthma's etiology, age of onset, and demographic characteristics. Data were collected from a geographically weighted random sample of the continental U.S. (1058 cases), in four seasonal cohorts (2005-2006). The study found that 12.9% of the sample report asthma, 11.6% report chemical hypersensitivity, and 31.4% of those with asthma report chemical hypersensitivity. Among asthmatics, 38% report irritation from scented products, 37.2% report health problems from air fresheners, and 13.6% report their asthma was caused by toxic exposure. Asthma cases affected each racial/ethic group in roughly the same proportion, with nearly 50% classified as childhood onset.