A back blister is a type of sore which appears on or in the skin, usually only involving the top layer or two of tissue. It is typically filled with fluid that is clear to honey-colored. Blisters may appear on the back for any number of reasons, but the most common is friction or a skin infection. Eventually, most blisters burst and the fluid drains out. After drainage has occurred, the back blister may crust over and form a scab before healing completely.

For most individuals, the formation of a back blister is an uncommon occurrence. Most blisters form in areas where friction can cause skin irritation, such as the backs of the heels or inner thighs. If friction is applied to the back during certain recreational activities or due to ill-fitting clothing, a back blister may occur. A blister can also occur due to certain bacteria, which can cause a skin infection in the top portion of tissue, primarily in pores or glands.

Bacterial infections are the most common cause of back blisters, as bacteria are present on the skin at all times. Staph bacteria is one of the most prevalent types on the skin, but streptococcus is also quite prominent. A condition known as impetigo is one potential cause of back sores or blisters. This is a skin infection which results in one of more blisters anywhere on the skin. They are usually thin and easy to pop or burst and are filled with a light colored fluid.

Other infections can cause more painful and severe back blisters. This type of skin infection may start out as a small blister-like sore and eventually grow into a large abscess. An abscess, or boil, is a sac of pus, debris, and dead skin which forms in a pore, hair follicle, or sweat gland. Although similar to a back blister, an abscess on the back is usually deeper in the skin and harder to get rid of. They may occur more frequently in those who shave or wax hair from their back.

An abscess eventually has to be drained of its fluid or pus before it can heal properly. This may happen on its own or it may have to be lanced by a doctor. The fluid from an abscess is often high contagious and malodorous and it may be yellow, green, clear, or brown in color. Sometimes antibiotics are given to prevent the spread of infection and to promote proper healing.

Anyone who has back blister that fails to heal, becomes severely painful, or is accompanied by several more blisters or skin irritation should contact a doctor. In most cases, blisters are minor annoyances that clear up without treatment. On occasion, a treatment-resistant strain of bacteria will be to blame and specialized medications will be needed.