Fennel can sometimes cause allergies, abdominal distension, loose stools, constipation, nausea and other bad things. 1. Fennel is both a traditional Chinese medicine and a condiment, with the efficacy of dispersing cold and relieving pain (relieving pain by removing cold from the body), regulating qi and stomach, it can be used in the treatment of menstrual cramps, cold pain in the abdomen, distension and pain in the epigastrium (abdomen), and vomiting and diarrhea, and it has no obvious side effects if it is used correctly under the guidance of a doctor. 2. Fennel is pungent and warm in nature, if overdose or yin deficiency and fire (deficiency of yin and essence in the body, hyperactive fire) people take it, there may be irritable heat (irritability and sultriness), night sweats (sweating abnormally after going to sleep, and waking up sweating stops), dizziness, insomnia and other uncomfortable symptoms. 3. Fennel has a special fragrance, and if you are not accustomed to the flavor of fennel, you may experience symptoms such as nausea and vomiting. If fennel is used in the treatment of diseases, it is recommended to use it with other medicinal herbs under the guidance of a doctor’s diagnosis, and should not be used on its own.