12 adult patients with perennial asthma and chronic skin infection were found to have immediate hypersensitivity to Trichophyton spp. 10 patients were tested by bronchial provocation and gave immediate bronchial reactions to an extract of T tonsurans. Double-blind, placebo-controlled nasal challenge of 8 patients demonstrated that the upper airways of these patients were also sensitive to this dermatophyte antigen. In addition to perennial asthma most of the patients had persistent eosinophilia and chronic rhinosinusitis. The results suggest that absorption of fungal antigen can give rise to IgE antibody production, sensitisation of the airways, and symptomatic asthma and rhinosinusitis. Several patients had many of the features of late onset or "intrinsic" asthma.