If you use potatoes externally to reduce swelling, usually use potatoes cut into thin slices and then applied externally to the local subcutaneous hematoma or trauma swollen parts, can promote the reduction of swelling, each time about 30-60min, can be applied 3-5 times a day is possible. If you want a better effect, you can use frozen potatoes or use potatoes stirred into puree and then applied externally, the contact surface will be more. If frozen, it can also achieve pain relief for acute bleeding or acute soft tissue injury. If there is a very obvious local epidermal break or wound, it is not recommended to use potatoes externally because it may induce wound infection.