Some moulds are useful to man.
Carefully cultivated varieties enhance the flavour of Camembert, and give blue and Roquefort cheeses their marbled appearance and characteristic tang. Probably the most famous beneficial mould is a Penicillium. The discovery of its ability to kill harmful bacteria led to the development of antibiotics and a whole new era in the treatment of disease. However, many moulds are a nuisance because they spoil food, clothing and leather, and cause extensive food crop losses in the form of blights and rusts. In addition, some moulds may pose a health hazard by producing substances called mycotoxins.