Alternaria sp. This fungus is a large universally occurring genus. Several form-species are found as saprophytes on dead and dying plant parts. Conidia of this fungus are easily carried by the wind. Commonly found in house dust, carpets, textiles, and on horizontal surfaces in building interiors and is one of the main fungal causes of allergy. Outdoors, it may be isolated from samples of soil, seeds and plants, and is frequently reported in air. The large spore size suggests that the spores from this fungus will deposit in the nose, mouth and upper respiratory tract causing nasal septum infections. It has also been associated with hypersensitivity pneumonitis. It is a common cause of extrinsic asthma. Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema. Baker's asthma is associated with inhalation of Alternaria conidia present in flour. Farmer's lung type of allergy has also been reported recently. Other diseases caused by Alternaria include mycotic keratitis, skin infections, and osteomyelitis. Also, the species Alternaria alternata is capable of producing tenuazonic acid and other toxic metabolites that may be associated with disease in humans or animals. Several species of Alternaria are pathogenic to plants. Morphological characteristics include abundant production of conidia that are large (18-83 x 7-18 microns) and multicellular with both transverse and longitudinal septa; conidiophores are dark, mostly simple.