Purpura is caused by the leakage of red blood cells from the blood vessels into the skin, connective tissue or mucous membranes and is a common type of bleeding disorder of the skin. Purpura occurs when the epidermis changes color and can become purplish or brownish red. Purpura can be classified as petechiae, petechiae and hematomas, and its classification is based on the area of color change. A bleeding area of 2-3 mm is called petechiae and a bleeding area of more than 0.5 cm is called petechiae. Purpura is usually not elevated above the skin surface, but only slightly elevated in the case of allergic purpura. The purpura is purplish red when it occurs and does not fade when pressed, then it gradually becomes lighter and fades to yellow in about two weeks. The main factors leading to purpura are abnormal platelet number or function (platelet distribution disorder, thrombocytopenia), abnormal blood vessel wall structure and function, abnormal coagulation, etc. According to different etiologies and clinical manifestations, it can be divided into many different types of purpura, such as simple purpura, allergic purpura, thrombocytopenic purpura, capillary dilated circumscribed purpura, rheumatic purpura, etc. Therefore, purpura is not a disease and a clinical symptom caused by platelet abnormalities and other reasons. In daily life, if symptoms such as small bleeding spots on the skin, bruises and petechiae, or blood oozing from the gums occur, it is recommended to consult a hematologist as soon as possible to find the cause of the disease and treat it symptomatically.