They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead to asthma.

They are present in the human mycobiome and readily cause opportunistic infections in immunocompromised people such as AIDS patients.

[2] At least 20% of agricultural spoilage is caused by Alternaria species, with the most severe losses reaching 80% of yield.

[2] Many human health disorders can be caused by these fungi, which grow on skin and mucous membranes, including on the eyeballs and within the respiratory tract.

Many species of alternaria modify their secondary metabolites by sulfoconjugation;[3] however, the role of this process is not yet understood.