Legs full of small red dots, may be leukemia, but more common in allergic purpura, primary immune thrombocytopenia and so on. 1. Small red dots on the skin can not be excepted leukemia, leukemia may also be manifested as hemorrhagic symptoms, bleeding spots on the lower limbs and hematuria and other symptoms, commonly found in middle-aged and elderly people, usually the routine blood test will show three series of abnormalities, with fever, fatigue, anemia and other manifestations. 2. Children or adolescents, especially males, small red dots appear on both legs, and repeated episodes, appear in batches, symmetrical distribution, varying shades, different sizes, fusion into a piece, and can gradually subside on their own within a few days, partly accompanied by abdominal pain, diarrhea, joint pain, hematuria, proteinuria, etc., the first consideration of purpura allergica. 3. In addition, primary immune thrombocytopenia, aplastic anemia, etc. will also appear skin petechiae ecchymosis. This condition should be timely medical care, find the cause of the disease, under the guidance of physicians targeted treatment.