Purple nails are considered to be a sign of trauma, gray nails, heart disease, chronic obstructive pulmonary disease and other diseases. 1. Trauma: when the patient’s fingernail area suffers from external impact caused by subnail hemorrhage, bruising, nails can be purple. 2. Gray nails: mainly caused by ringworm infection, the patient’s nail plate can be cloudy, thickening, discoloration, atrophy, shedding, uneven surface of the nail, etc., and the nails can be purple, white, yellow and so on. 3. Heart disease: the disease is related to heredity and congenital developmental defects. Typical symptoms of patients include panic, palpitations (rapid heartbeat, often accompanied by panic), shortness of breath, swelling of hands and feet, etc. Nails may also be purple due to insufficient blood oxygen. 4. Chronic Obstructive Pulmonary Disease (COPD): The disease can also cause some patients to have purple nails, which are easily accompanied by other symptoms such as dyspnea, cough and sputum. The cause of the disease is still unclear, may be related to genetic factors, bronchial asthma and other diseases. Purple nails are also considered to be emphysema, pulmonary embolism and other signs of the disease, it is recommended to consult a doctor for examination in order to clarify the disease and follow the doctor’s instructions for treatment.