Vomiting during menstruation is mainly due to bleeding caused by the shedding of the endometrium during menstruation. The amount of prostaglandins secreted when the endometrium is shed varies from one individual to another. When the amount of prostaglandins secreted is low, it does not cause pain in the lower abdomen and does not lead to other symptoms. When more prostaglandins are secreted, it may cause contraction of the smooth muscle of the uterus and also the smooth muscle of the gastrointestinal tract, and you will experience nausea and vomiting. You can take oral vitamin B6 to effectively relieve vomiting. It is advisable to eat easily digestible food when you have your period to reduce the burden on your gastrointestinal tract.