Mycotoxins are toxic secondary metabolites produced by fungi that can cause disease and death in both humans and animals. They are low-molecular-weight natural products produced as secondary metabolites by filamentous fungi and are toxigenically and chemically heterogeneous. Several hundred different mycotoxins have been identified, but the most commonly observed mycotoxins that present a concern to human health and livestock include aflatoxins, ochratoxin A, patulin, fumonisins, zearalenone, and nivalenol/deoxynivalenol. Mycotoxins can appear in the food chain as a result of mold infection of crops both before and after harvest. They can be toxic when ingested, inhaled, or absorbed into the skin, and can cause acute and chronic health effects. Mycotoxicosis is the term used for poisoning associated with exposures to mycotoxins. Testing for mycotoxicosis can be conducted using immunoaffinity columns. To minimize the health risk from mycotoxins, people are advised to avoid moldy food, store food properly, and maintain proper hygiene.