Most blisters on the feet are caused by friction and do not require medical attention. New skin will form underneath the affected area and the fluid built up in the blister is simply absorbed back into the tissue. You can soothe ordinary blisters with vitamin E ointment or an aloe-based cream.
Do not puncture a blister unless it is large, painful, or likely to be further irritated. If you have to pop a blister, use a sterilized needle. Wash the area thoroughly, then make a small hole and gently squeeze out the clear fluid. Apply a dab triple antibiotic ointment/cream to help protect against infection. Do not remove the skin over a broken blister. The new skin underneath needs this protective cover. Cover the area with a bandage and mild compression.
If the fluid is white or yellow, the blister is infected and needs medical attention.
You can prevent blisters by breaking in new shoes gradually, and putting petroleum jelly or an adhesive bandage on areas that take the rub -- before the blister happens. Wear socks that have heels instead of tube socks (they bunch up and cause blisters). Acrylic and other synthetic-fiber socks are good choices. Be sure to wash and dry your feet daily to prevent bacterial infections, or Athlete's Foot.