Aspergillus penicillioides is a fungus of the genus Aspergillus, and is among the most xerophilic fungi. Aspergillus penicillioides is typically found in indoor air, house dust, and on substrates with low water activity, such as dried food, foxy papers and binocular lenses. The distribution of the fungus is worldwide as it has been found in bed dusts from maritime temperate, Mediterranean, and tropical climates. The abundance of the fungus is influenced by outdoor climate, with highest numbers found in tropics and lowest numbers in Mediterranean climate. Cool temperature tends to decrease number of A. penicillioides in house dusts.