Aureobasidium pullulans is an ubiquitous saprophyte mould, which is generally considered as an environmental contaminant. It is most common in temperate zones, found in forest soil, freshwater, aerial portions and on leaf surfaces of plants as well as on seeds (wheat), cereals (barley, oats) and some nuts such as pecans. It is also found as spoilage agent on fruits (pears, grapes and tomatoes) or in fruit drinks. It has been associated with the deterioration of pears and oranges in storage or in transit. Chronic human exposure to A. pullulans via humidifiers or air conditioners can lead to hypersensitivity pneumonitis (extrinsic allergic alveolitis) or “humidifier lung”.