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A blister is a bubble of fluid that builds up between two layers of skin. The most common cause of blisters is physical friction.
You might get a friction blister from wearing a new pair of shoes or wearing shoes that are too tight, for example. Other causes of blisters include burns, certain types of eczema (an inflammatory skin condition), and the herpes simplex virus.
Most blisters will heal when left alone and are very unlikely to become infected. If you decide to pop a blister, though, you increase your risk of infection. A few key signs can signal that a blister is infected.
This article will discuss the signs of an infected blister, complications of infection, how to treat a blister, and when to call a doctor.
Your blister may be infected if it’s:
- Increasingly painful
- Red, especially if red streak marks are radiating outward
- Draining pus
- Warm to the touch
- Causing you to develop a fever
A blister can become infected if it bursts prematurely (or you pop it open), and bacteria are introduced into the wound. Depending on the bacteria causing the infection, symptoms may vary in severity.
Cellulitis is an infection of the deeper layers of the skin. The condition is caused by various types of bacteria—most commonly, group A Streptococcus.
Signs of this type of infection include:
- Skin that’s warm to the touch
You have an increased risk of contracting cellulitis if you have chronic edema (tissue swelling).
To treat this infection, doctors will prescribe oral antibiotics. If the infection has been left untreated, intravenous (IV) antibiotics may be necessary. If left untreated, cellulitis can lead to complications such as endocarditis (infection of the inner surface of the heart) or bacteremia (infection in the bloodstream).
Sepsis, or bacteremia, is an infection that occurs when bacteria end up in the bloodstream. This can happen when an infected skin wound is left untreated. When it reaches the bloodstream, the infection begins to affect your entire body.
Antibiotic treatment is necessary to prevent complications of sepsis such as septic shock (a severe reaction to infection), which is a potentially fatal condition.
Properly caring for a blister can help prevent infection. But you should monitor it for signs that you need to contact a healthcare professional.
If you note any signs of infection, lightly apply an antibiotic ointment to the inflamed area and cover it with a clean bandage. Call your healthcare professional for advice. Do not ignore these signs.
When to See a Doctor
If you notice any signs of infection, call your healthcare professional to arrange for treatment. An infected blister may require prescription antibiotics and professional wound care.
You should also see a doctor if your blister (or blisters):
- Keeps coming back
- Is in a sensitive area such as the eyes
- Is one of many and has come on suddenly
- Happens because of an allergic reaction
- Happens due to a burn injury
If you get a blister, caring for it properly can help avoid infection. Ideally, you should:
- Gently clean the area of the blister.
- Cover it loosely with a bandage. Use padded bandages or create a donut-shaped dressing around the blister to prevent putting pressure on the blister.
- Avoid irritating the area further or getting it dirty.
- Replace the bandage daily or if it gets soiled. Ensure the blister is healing and doesn't have signs of infection.
If a blister pops on its own, gently cleanse the area and try not to remove the skin "roof" of the blister. Apply a dab of petroleum jelly. Cover with a bandage to protect it while it heals. A gel (hydrocolloid) bandage can help reduce the pain from the open wound.
Popping a blister can increase the risk of infection, so only drain it if it’s really big and painful. Avoid popping any blister other than a friction blister.
Most friction blisters will go away on their own. However, sometimes, they can burst open on their own before the wound is fully healed. This can lead to infection. In addition, not taking proper hygiene measures when popping a blister can also cause it to become infected.
Signs of infection include pain, swelling, redness, red streaks, heat, and pus drainage. You may also have a fever if your wound is infected. If you notice your blister is getting worse and seems infected, you should make an appointment with your healthcare professional.
A Word From Verywell
Most skin wounds go away on their own. But in some cases, they can become infected. To prevent an infection from happening in the first place, avoid popping blisters and keep the area clean. And if you have to touch your blisters, always make sure to wash your hands before doing so.
Are you worried that your blister is infected but not sure whether it actually is? Call your doctor’s office or contact a telehealth service for advice.
Frequently Asked Questions
- How long does it take an infected blister to heal?
Depending on the size and location, a normal blister will heal in about a week or so. If your blister becomes infected, expect the healing process to take longer.
- Should you cover a blister or leave it uncovered?
You should cover a blister to prevent further irritation to the skin. Donut-shaped bandages help pad and protect the area.
- How can you tell if a blister is infected?
A blister is likely infected if it’s swollen, red, and painful. You may also notice that it’s hot to the touch. Sometimes, pus will drain from the area. In the case of a severe infection, you may develop a fever.