Alternaria alternata is mainly an outdoor fungus whose spores disseminate in warm, dry air, so in temperate climates, their count peaks in the summers. Alternaria may also be found in damp, insufficiently ventilated houses, where its allergenic properties cocreate the sick building syndrome. The allergenic extracts from Alternaria hyphae and spores still remain in use but are variable and insufficiently standardized as they are often a random mixture of allergenic ingredients and coincidental impurities.