Mycotoxins are secondary metabolites produced by fungi and can grow on a variety of crops including cannabis. Mycotoxins may cause a variety of adverse health effects ranging from acute poisoning to long-term effects such as immune deficiency and cancer.

Development of fungal spores can occur naturally, due to poor handling during cultivation, during other manufacturing processes, and/or subsequent stages of transportation and poor storage practices when conditions favour their growth. Mycotoxins can also end up in extracts and cannabis products thus their testing is important to ensure consumer safety.