Mold
Mold spores float outdoors for much of the year and grow indoors wherever it stays damp. 3 guides, each with its sources.
Alternaria (mainly Alternaria alternata)AlternariaAn outdoor mold whose spores peak in summer and fall. Allergy to it is closely tied to asthma, including severe asthma.CladosporiumCladosporiumOne of the most common molds in outdoor and indoor air. Its spores can cause hay fever symptoms and are linked with asthma flare-ups.Aspergillus (including Aspergillus fumigatus)AspergillusA common mold indoors and outdoors. It can cause allergy symptoms and, in some people with asthma or cystic fibrosis, a lung condition called ABPA.