If a red blood spot suddenly appears on the skin after contact with a substance, it may be caused by an allergic reaction of the body, usually accompanied by itching symptoms, if it is not serious, it can be temporarily observed and can subside with time. If the lesions continue to develop or other accompanying symptoms appear, it is recommended to consult a doctor promptly for specific treatment, such as taking anti-allergy drugs, commonly used paracetamol, benadryl, etc. If the blood spot has been present recently, it is necessary to consider whether it is caused by a disease. Common causes 1, hemangioma: It is a benign tumor caused by abnormal vascular tissue, and the cause is still unclear. They are red nodules with clear borders and varying sizes above the skin. 2. Purpura-like diseases: they are a group of diseases with subcutaneous bleeding as the main symptom, and can be divided into allergic purpura, thrombocytopenic purpura and so on. It is mainly caused by abnormal blood vessel wall, abnormal platelets or abnormal coagulation mechanism. It is often manifested as purple and red lesions appearing on the surface of the skin, which do not appear to fade in color after pressure, and may also be accompanied by nosebleeds and gum bleeding. Treatment method 1, hemangioma: For hemangioma without other symptoms and increasing trend, it can continue to be observed and some of them can disappear by themselves. If there are other symptoms or tendency of enlargement, blood routine and ultrasound examination can be improved, and the doctor can judge and treat according to the specific situation. Propranolol ointment and imiquimod cream can be applied to the affected area to help the lesions subside. You can also take propranolol orally to promote vasoconstriction. 2. Purpura-like diseases: If patients are suspected of having such diseases, they need to seek medical attention to improve capillary fragility test, prothrombin time measurement and other related examinations. After the cause is clearly identified, the cause should be treated promptly, for example, patients with allergic purpura can apply glucocorticoids, such as prednisone, dexamethasone, and immunosuppressants, such as cyclophosphamide, cyclosporine, etc. In addition, in daily life, patients should pay attention to the prevention of falls and strengthen the nutrition of the body. Precautions For patients with red blood spots on the skin, attention should be paid to timely medical consultation, as well as daily local skin care and avoid external stimulation.