A scratch on the body broke the skin and bleeding, the first thing to find the cause, there may be skin diseases, there may be blood system diseases caused, should be for the cause of bleeding, and then choose the right method of treatment. A, dermatological diseases: 1, papular urticaria: papular urticaria is mostly due to mosquitoes, mites and other bites, the release of some venom, stimulating human skin papule-like changes, accompanied by itching symptoms, because of itching human reflexive scratching, it will break the skin and bleeding. It is recommended to keep the indoor environment hygienic and well ventilated. You can disinfect locally, apply anti-allergy ointment, such as compound flumethasone ointment, trimethoprim econazole cream, etc. Severe cases can be combined with oral medication, such as loratadine, benadryl hydrochloride, etc.; 2. Contact dermatitis: most of them are allergic reactions caused by skin contact with exogenous material stimuli, divided into plant material irritants, chemical sensitizers, animal sensitizers. The common ones are plant flowers, various detergents, bleaching powder, pesticides, etc.. The main manifestations can be erythema, swelling, papular rash, accompanied by itching, etc. It may also appear that the skin on the body will break and bleed when it is scratched. It is recommended to remove the allergen immediately, and oral anti-allergy drugs such as loratadine can be taken. At the same time can be used topical glucocorticoid drugs, such as halomethasone cream, dinaide cream, etc.; 3, drug dermatitis: refers to drugs through oral, intramuscular injection, static injection, etc., into the body resulting in allergic reactions, often drug rash, dermatitis, can lead to a scratch on the body to break the skin bleeding. It is recommended to stop all suspected allergenic substances, intravenous injection of hydrocortisone, vitamin C, calcium and other drugs, and if there is skin mucous membrane damage, topical erythromycin ointment and other drugs can be used. Second, the blood system diseases: 1, thrombocytopenic purpura: is a bleeding disease characterized by thrombocytopenia, manifested as spontaneous skin mucous membrane bleeding, for punctate bleeding or sheet bleeding, there may be a scratch to break the skin bleeding situation. You should go to the hospital and use glucocorticoids such as methylprednisolone under the guidance of a doctor, you can also use high-dose intravenous human immunoglobulin, and if necessary, you can also choose plasma replacement therapy; 2. Simple purpura: a bleeding disorder caused by vascular abnormalities, often manifested as spontaneous recurrent petechiae, petechiae. It is often found in the menstrual period of women, and is related to the secretion of hormone level in the body and abnormal platelet function, so it also leads to the symptom of bleeding when the skin is broken when it is scratched, which usually does not require special treatment and can heal itself. However, it is necessary to pay attention to the hygiene of the skin surface and to avoid infection caused by excessive scratching. In summary, the treatment is not exactly the same for different causes of the disease. You should go to the hospital to do allergic reaction tests to find allergens, and also blood analysis tests, after a clear diagnosis, under the guidance of doctors to use drugs.