02/03/2026
Alternaria is one of the most common types of house mold, with over 250 species. Indoor Alternaria spores usually originate outdoors and multiply in carpets, wallpaper, textiles, window frames, and HVAC systems. Like all mold, it grows in damp and humid areas, reaching maturity in just five days. This type has a velvety texture with dark green or brown hairs.
Those with health problems such as pulmonary diseases, asthma, weak immune systems, and allergies are most vulnerable to this mold. Prolonged exposure to Alternaria has been linked to the onset of asthma in children, while allergies wrought on by its spores are more pronounced in spring and summer. This type of mold habitually lingers in the air on dry, windy days and, when inside, can grow under carpeting and inside walls in some cases.