Rashes, pimples, sores and other skin disruptions appear and disappear frequently. Any number of problems could cause a sore and blister to appear on your back, from a boil to an outbreak of shingles. Friction can cause irritated areas and blisters as well; wearing athletic equipment such as shoulder pads or other clothing that rubs against your skin could cause a sore and blister. See your doctor if you have a sore that blisters, especially if redness, pus or swelling develops at the site.
If you wear clothing or equipment that fits tightly or that slides back and forth, you could develop a blister at the site. Normally, an irritated site appears red at first. If irritation continues, the top layer of skin begins to separate from the layer beneath. The accumulation of fluid between the layers creates a blister. While most clothing doesn't rub across your back, sport equipment such as football pads can, especially if not properly fitted. Watch for areas of redness or sores that indicate your equipment doesn't fit correctly. Blisters normally resolve within a few days once you stop irritation in the area. Call your doctor if the area becomes increasingly reddened, if you run a fever or have other signs of infection.
If you had chicken pox in the past, you carry the herpes zoster virus dormant in your tissues. Later in life, stress or trauma can reactivate the virus, causing shingles. Nearly 33 percent of Americans develop shingles at some point, the Centers for Disease Control and Prevention note; nearly half of them are over age 60 at the time of an outbreak. Shingles causes small blistering sores to appear along nerve paths, often developing as a stripe around the left or right side of the body, including the back. Like chicken pox, shingles causes fluid-filled blisters that break and scab over.
Staph infections of the skin can cause furuncles, better known as boils. Infections that develop around hair follicles, boils often start when bacteria enter a break in the skin, such as a scrape or other injury. The area forms a painful, reddened blister-like structure filled with pus. Applying warm compresses may help the boil open and release the pus. In some cases, your doctor may incise the boil and drain it. Antibiotics may be necessary in some cases.
The chronic condition dermatitis herpetiformis causes extremely itchy blisters and red areas on the skin, often on the back. You may have a burning feeling in the area before blisters appear. Each outbreak lasts one to two weeks before healing. Gluten allergy causes this disorder, which occurs more commonly in men and people of northern European ancestry. Between 10 and 20 percent of people with this condition do experience remission, according to the American Osteopathic College of Dermatology. Following a gluten-free diet cures the disorder, but it can take months for lesions to stop appearing.