The most common clinical cause of stomach pain on the 3rd day of menstruation is due to drinking cold drinks or eating cold foods during menstruation, or eating foods that should not be eaten, such as winter melon, barley, carrots, watermelon, pears, bananas, and other foods that cause menstrual pain. In addition, cold drinks or frozen foods can cause vasoconstriction, which causes the blood vessels in the uterus to constrict as well, thus causing pain in the lower abdomen. Therefore, it is important to give warmth during menstruation and not to eat cold foods or drink frozen beverages. In addition, if you have stomach pain, it is recommended to drink a cup of hot brown sugar water to relieve lower abdominal pain and have the effect of expelling cold and warming the uterus. It is best to go to the hospital for an ultrasound examination after the menstruation is clean to rule out organic lesions.