Afairly common outdoor mold is called Alternaria. Alternaria grows on decaying vegetation and produces large spores which are full of allergens (ie. proteins or other biochemicals which trigger allergic reactions). Alternaria can also grow indoors. Levels of Alternaria tend to peak in summer and early fall.
A number of studies have linked high levels of Alternaria in the air to higher levels of severe asthma attacks and nasal problems. Researchers have found genes which make people more sensitive to Alternaria and other molds. Sensitivity to Alternaria is often tested in doctors offices by the use of skin or blood tests.
Much more research on the effects of certain molds on asthma and sinus problems is needed. A good article on the effects of Alternaria on asthma was written by Knutsen et al. and is now in press in the journal Allergy