Trematodes are flatworms that can settle in different organs of the human body, particularly the liver, bile ducts, lungs, and intestinal system. Among these, Paragonimus westermani, found in the Trogiotrematidae family, is known as the lung fluke and infects humans through the consumption of raw or undercooked crab meat. Fasciolopsis buski, a different family of intestinal flukes, is a giant intestinal fluke that causes serious damage, particularly in the duodenum and jejunum of humans and pigs. Heterophyes heterophyes is the smallest intestinal fluke and causes irritation in the intestinal mucosa. Metagonimus yokogawai is an intestinal parasite commonly found in animals in many parts of the world. Echinostoma species are parasites found in countries where it is customary to eat gastropods without cooking them. Gastrodiscoides hominis and Watsonius watsoni are parasites known as flukes of the stomach and intestines, causing damage to the large intestine when metacercal aquatic plants are eaten raw. This review emphasizes the importance of the ‘butterfly effect’ created by lung and intestinal trematodes in the human body, despite their small size, in terms of public health.