Ten-year-old girls with blood spots on their pants, sometimes not, may be caused by the first menstruation, anal fissure, should immediately go to the hospital to identify the cause. 1. Menstruation: Menarche refers to the first menstruation of a girl, and the age of most girls’ menarche is usually around 12 to 13 years old, with obvious differences between different individuals, and the time of menarche is either early or late. Early or late menarche is genetically linked, with mothers having early menarche and their daughters having early menarche as well. When a girl has her first menstrual period, her underwear will be stained with blood. 2. Anal fissure: Anal fissure is a tear or rupture of the skin of the anal canal, which is often associated with constipation, trauma and microbial infection. When a child has an anal fissure, he or she may experience pain and itching in the anus, or blood in the stool, and some of the blood will fall onto the underwear, leaving blood spots. Children should be seen immediately when they become unwell.