A little blood in a ten and a half year old girl may be menarche, or vaginal bleeding due to urinary tract infection or hymen rupture. 1. Menarche. The age of girls’ menarche is generally around 11 to 14 years old, but due to genetic factors, nutritional status and different development of the body, the specific time of menstruation there are individual differences. Ten and a half year old girl to a little blood is likely to be the first menstrual manifestations, due to the first menstrual hormone levels are not stable, may be only a small amount of bleeding, is a normal physiological phenomenon. 2. Urinary system infection. Ten and a half years old girl to a little blood may also be caused by urinary tract infection, such as urethritis, cystitis, inflammation of the urinary system will appear after the invasion of urinary urgency, urinary frequency, urinary bleeding symptoms, a small amount of bleeding may be caused by urinary infection. 3. Hymen rupture. Some girls in strenuous exercise or cycling, trauma impact will appear after a small amount of bleeding phenomenon, may be hymen damage rupture caused by bleeding, usually accompanied by vaginal pain. Ten and a half year old girls come a little blood may be normal menarche, may also be caused by disease, it is recommended that timely consultation to identify the cause.