Purple coloring of the fingernail cap is commonly caused by trauma, poor blood circulation, hemangioblastoma and Raynaud’s disease. Trauma is the most common cause of purple fingernails. When the fingers are pinched or smashed, the blood vessels under the nail bed will rupture and bleed, resulting in purple fingernails. Poor blood circulation at the end of the finger, resulting in local ischemia and hypoxia can also cause purple fingernail caps. Cardiovascular, respiratory and pulmonary diseases may cause the mixing of arterial and venous blood in the blood, leading to a decrease in blood oxygen saturation, causing purple fingernails. Hemangioblastoma is a benign subnail tumor that develops underneath the nail bed and appears as purple nodules underneath the nail plate, causing the fingernail cover to appear purple. In addition, because people with Raynaud’s disease themselves have peripheral vascular circulatory disorders of the extremities, mainly caused by arterial spasm, peripheral circulatory disorders, usually in the episodic period of manifestation of the finger cap or the whole finger purple, black. If you are not feeling well, you should go to the hospital in time to find out the cause and follow the doctor’s instructions to standardize the treatment, so as not to delay the condition.