Purple blood blisters on the soles of the feet are considered to be caused by friction and diabetic gangrene. 1. Friction: if the shoes are not suitable or a lot of walking will cause purple blood blisters due to friction, if the blood blisters are small, they can be absorbed by themselves, if the blisters are big, you should go to the hospital, the doctor will use the sterilized needle to puncture them, so that the liquid inside will flow out, usually you should choose loose and comfortable shoes, avoid walking for a long time. 2. Diabetic gangrene: this is a complication of diabetes, in the beginning of the lesion will also appear purple blood blisters, this time should be active control of blood glucose, blood glucose control in a reasonable range, the local use of wet dressings or closed negative pressure wound treatment, at the same time, intravenous ceftriaxone sodium and other control of infection. Purple blood blisters on the soles of the feet and other reasons (such as trauma), to consult a doctor in a timely manner, such as the need for medication should also be used in accordance with the doctor’s instructions, to avoid delaying the condition.