New winter boots, a long day on snowshoes, or a fall hike in boots you haven't worn since spring. Any of these can leave you with a sore, fluid-filled bubble on your heel or toe. Blisters are one of the most common foot problems for active people. Researchers have studied them in runners, hikers, military trainees and ultramarathon racers.3

Most blisters are a nuisance that heals on its own. But for some people, especially people with diabetes, a small blister can turn into a bigger problem. Here's why blisters form, how to lower your chances of getting one, how to care for one, and when to get help.

When a blister needs prompt attention: If you have diabetes, numbness in your feet or poor circulation and you find a blister, don't wait for your next appointment.4,5 Also get care for a blister that shows signs of infection (pus, red streaks, or skin around it that is hot, swollen or more painful) or a blister caused by a burn or frostbite.1,2 Call us instead of using the web form: Butte & Anaconda (406) 782-2278, Bozeman, Ennis & Harlowton (406) 587-8478. For a spreading infection with fever, or severe symptoms, seek emergency care.

What Is a Blister, and Why Do Feet Get Them?

A blister is a pocket of fluid that collects between layers of skin. It forms under the epidermis, the top layer. The fluid is usually clear, but it can be blood if deeper tissue was pinched.2 Feet and hands are the most common places to get them.2

Cleveland Clinic lists three main types:2

  • Friction blisters from repeated rubbing, such as walking a lot in shoes that fit poorly or going without socks.
  • Blood blisters from pinching that damages small blood vessels.
  • Heat blisters from burns or sunburn. They can also form as skin warms up after frostbite.

Foot blisters are usually the friction kind. A 2024 review in the Journal of Athletic Training explains that it's not just the sock rubbing your skin. As you walk, the bones in your foot move while the skin on the surface stays stuck to the sock or boot. That repeated pulling, called shear, eventually tears the skin's top layer and lets fluid fill the gap.3 The authors note that blisters tend to show up over bony, high-pressure spots: the back of the heel, the toes, the big toe and the ball of the foot behind it.3 They also note that most blisters happen early in a new activity or training program, before the skin has adapted.3

How Can I Prevent Blisters?

Common advice from dermatologists and other health sources includes:

  • Get the fit right. Shoes and boots shouldn't be too tight or too loose.1
  • Break in new footwear slowly. Cleveland Clinic recommends breaking in new shoes gradually.2 The CDC suggests starting with an hour or two a day.5 That's worth remembering before a long day in new pac boots or hiking boots.
  • Choose your socks with care. The American Academy of Dermatology (AAD) suggests nylon or moisture-wicking socks, and two pairs if one isn't enough.1 For other clothing during activity, it suggests moisture-wicking fabrics rather than cotton, which holds sweat.1
  • Protect hot spots. Moleskin or another soft bandage on problem areas can help, as long as it's applied securely.1
  • Stop when it starts. AAD advises stopping your activity right away if you feel pain or discomfort, or if your skin turns red.1

It's fair to say the research here is mixed. The 2024 review found that densely padded acrylic socks were better than cotton in two studies, and some cushioned insoles helped in others. But evidence on powders, antiperspirants, double socks and taping was weak or conflicting. Footwear fit is widely blamed, but it hasn't been tested directly in studies.3 In short, the basics above are reasonable, but no single product is proven to stop every blister.

Should I Pop My Blister?

Usually, no. The skin covering a blister (its "roof") protects the raw skin underneath from infection.2 AAD advises against popping or draining blisters because it can lead to infection.1

AAD does say a blister that is large and very painful may be drained carefully. Its steps: sterilize a small needle with rubbing alcohol, pierce the blister at one edge to let the fluid out, then wash the area with soap and water, apply petroleum jelly and keep it covered. Leave the roof in place.1 If you have diabetes or poor circulation, don't do this at home. See a provider instead.4,5

How Do I Take Care of a Blister?

  • Keep it clean. Wash gently with mild soap.2
  • Cover it. Loosely cover it with a bandage.1 Cleveland Clinic suggests an antibacterial ointment under the bandage or gauze, changed at least once a day.2
  • Take the pressure off. For blisters on the bottom of the foot, AAD suggests cutting padding into a donut shape, placing it around the blister, and covering both with a bandage.1 Wearing different shoes while it heals can help too.2
  • Give it time. Cleveland Clinic says most blisters heal in a few days.2 AAD says one to two weeks, and advises not going back to the activity that caused it until it heals.1

How Do I Know if a Blister Is Infected?

Watch for:1,2

  • Pus, or yellowish or greenish fluid instead of clear fluid or blood
  • Redness and swelling around the blister
  • Skin around it that feels hot or is getting more painful
  • Red streaks spreading from the blister

Cleveland Clinic also advises seeing a provider if a blister doesn't improve after a few days, or if it came from a burn or frostbite.2 If cold injuries are a concern this winter, our article on frostbite and chilblains explains the warning signs.

Why Are Blisters a Bigger Deal With Diabetes?

Diabetes can damage the nerves in your feet. When that happens, you may not feel a pebble in your sock or a blister forming.4 The CDC notes that if you don't feel pain in your feet, a cut, blister or sore can go unnoticed, and small problems can become serious if they aren't treated early.5 Reduced blood flow to the feet can also make it hard for a sore or infection to heal.4

That's why health agencies recommend these habits for people with diabetes:4,5

  • Check your feet every day, including between your toes. Use a mirror or ask a family member if you can't see the bottoms of your feet.
  • Wear shoes and socks at all times, even indoors. Check inside your shoes for objects before putting them on.
  • Break in new shoes slowly.
  • See your doctor or foot doctor right away for a blister, sore or ulcer. NIDDK also advises calling your provider for a blister that doesn't start to heal after a few days.

Learn more about diabetic foot care and why regular foot exams matter.

The Bottom Line

Most foot blisters come from repeated rubbing and shear, often in new or poorly fitting footwear. Well-fitting boots, good socks, breaking footwear in slowly and stopping at the first hot spot are sensible ways to lower your risk. Leave most blisters intact, keep them clean and padded, and watch for infection. If you have diabetes, numbness or poor circulation, treat any blister as a reason to call.

If blisters keep coming back in the same spot, a podiatrist can look at your feet and footwear and talk with you about why. Request an appointment and our team will follow up within one business day. You can also find your nearest office on our locations page.

This article is for general education and isn't a substitute for medical advice. Talk with a podiatrist or your doctor about your own symptoms.

Sources

  1. How to Prevent and Treat Blisters. American Academy of Dermatology (AAD). www.aad.org
  2. Blisters: Causes, Treatment & Prevention. Cleveland Clinic. my.clevelandclinic.org
  3. Rushton R, Richie D. Friction Blisters of the Feet: A Critical Assessment of Current Prevention Strategies. Journal of Athletic Training. 2024;59(1):8–21. pmc.ncbi.nlm.nih.gov
  4. Diabetes & Foot Problems. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). www.niddk.nih.gov
  5. Your Feet and Diabetes. Centers for Disease Control and Prevention (CDC). www.cdc.gov