There is blood on the underwear, but wiping with paper shows no abnormalities.

In general, blood stains on underwear without visible bleeding when wiping with paper may be caused by physiological or pathological factors, such as vaginitis or vulvitis. Specific details are as follows:

1. Physiological Factors

If the genital area is bitten by insects, the insects may draw blood from the skin, resulting in blood stains on underwear. This is considered a normal physiological phenomenon. In such cases, changing to clean underwear and maintaining good external genital hygiene is sufficient.

2. Pathological Factors

1) Vaginitis
Poor intimate hygiene may make the area susceptible to bacterial infection, leading to swelling of the vaginal mucosa. Sexual intercourse may then cause mucosal rupture and bleeding, often accompanied by itching of the external genitalia. Treatment may include vaginal suppositories such as metronidazole suppositories, tinidazole suppositories, or Baofukang suppositories, used under medical guidance.

2) Vulvitis
Wearing low-quality or tight-fitting underwear can cause repeated friction on the vulvar area, leading to local skin damage and possibly exudation of inflammatory fluid. It is recommended to take medications such as amoxicillin capsules, penicillin V potassium tablets, or cefuroxime axetil tablets under a doctor's supervision.

Besides the above common causes, blood stains may also result from hemorrhoids, endometritis, cervicitis, or other conditions. During treatment, it is important to maintain genital cleanliness, wear loose and comfortable underwear, and seek timely medical attention if symptoms are severe.