Most blisters are caused by friction or minor burns and do not require medical attention. New skin will form underneath the affected area and the fluid is simply absorbed. 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 or razor blade (to sterilize it, put the point or edge in a flame until it is red hot, or rinse it in alcohol). Wash the area thoroughly, then make a small hole and gently squeeze out the clear fluid. Apply a dab of hydrogen peroxide to help protect against infection.
If the fluid is white or yellow, the blister is infected and needs medical attention. Do not remove the skin over a broken blister. The new skin underneath needs this protective cover.
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.
Also, wear socks that have heels instead of tube socks (they bunch up and cause blisters). Acrylic and other synthetic-fiber socks are good choices. Because they don't breathe as well as natural fibers, however, you should wash and dry your feet after wearing them to prevent Athlete's foot.