||Description: Sporulating, filamentous / hyphae fungus (Alternaria alternata). Filamentous hyphae are seen here producing conidiophores with condia / spores at their tips. Alternaria is a dematiaceous (phaeoid; black pigmented mold) fungus commonly isolated from plants, soil, food, and indoor building environments. These molds are characterized by their dark pigmentation due to melanin, which effectively absorbs harmful UV-radiation and protects the organisms from fatal damage caused by radiation. They are causative agents of phaeohyphomycosis and other respiratory allergies. A. alternata is an allergenic fungus that is one of the main fungal causes of allergy, being a common type I & III allergen. Alternaria alternata is a cause of both allergic rhinitis (hay fever) in which inflammation of the mucous membrane of the nose occurs and of allergic asthma. It is the most common species isolated from human infections. Cases of onychomycosis, sinusitis, ulcerated cutaneous infections, and keratitis, as well as visceral infections and osteomyelitis have been reported. Alternaria is commonly found in house dust, carpets, textiles, on horizontal surfaces in building interiors, and window frames. Alternaria alternata also causes leaf spots, rots and blights in plants.