There are many types of fungi that produce secondary metabolites called mycotoxins. These compounds are very dangerous to humans and animals, as exposure to them causes acute or chronic toxicity. Temperature, humidity and pH are important environmental factors in the production of mycotoxins. There are about 500 types of mycotoxins that are found in many agricultural products such as peanut, cereals, wines, fruit juice, dried fruits, feed, and other foodstuffs. Among the most important genera of fungi that produce mycotoxins are Aspergillus, Penicillium, Altenaria, Fusarium, and others. Some of them infect plants in the field and produce mycotoxin, while others infect agricultural crops, foodstuffs, and feed in the store and produce mycotoxin during storage conditions. Mycotoxins are divided into various groups according to the degree of their impact and danger, into highly toxic, low toxic, carcinogenic, and mutagenic. This is depends on the chemical composition of the different types of mycotoxins, which are an open hydrocarbon chain with low molecular weights ranging between 100 and 697 Da. The biological effects of mycotoxins include damage to living tissues, suppression of immunity, and neurological disorders. Aflatoxins are one of the most dangerous mycotoxins as they are the main cause of hepatocellular carcinoma and the fifth most common carcinogen in the world.