Characteristics: Common allergen Type I, occasional pathogen, not known to be toxigenic.
Description: Exserohilum species are common, and are most closely related to Drechslera and Bipolaris. Our laboratory does not separate Bipolaris, Drechslera, and Exserohilum species. The only morphological difference between Bipolaris and Drechslera is that Drechslera spores germinate from all cells (of the spore) and Bipolaris germinates only from polar cells. Exserohilum spores have an inner cup-like structure which is visible in the basal cell. As an allergen, it has been known to cause Type I symptoms of hay fever and asthma. As a pathogen, it has rarely been known to cause phaeohyphomycosis (keratitis, sinusitis, and osteomyelitis) most often occurring in immunocompromised persons, although infections also occur in normal hosts. One case of brain abscess reported in an immunocompromised patient. It is not considered a toxigenic agent.