For many peoples, natural products are safe and without adverse effects for our health. For other people all natural chemicals found in food are less toxic than synthetic chemicals. However, there are just two of the persistent myths found on the Internet. Actually, potent and dangerous natural toxins can be formed in food in several ways (as defense mechanism of plants, for instance) and can cause several health effects ranging from abdominal cramps, nausea, vomiting, diarrhoea to allergic reactions. This paper presents the most important class of natural toxins as well as health and safety issues associated with their consumption.