You’ve probably felt that spot on your toe, ankle, or heel heat up. A bubble starts growing and spreading, while thin layers of skin shred and tear: A blister is imminent.
These small pockets of fluid are a frequent nuisance among hikers, runners, backpackers, and anyone who’s ever gone out in new shoes without breaking them in first. But blisters don’t have to mean the end of an outing. On the contrary, this type of wound is easy to prevent and treat if you just give it proper attention early on.
How do blisters form?
To prevent and treat them, it’s helpful to understand how blisters form. These painful bubbles occur when external forces cause the bone and skin to move out of sync, resulting in a tear under the surface, says Robin Larson, wilderness medicine program supervisor at the National Outdoor Leadership School.
The constant friction in a specific area caused by an ill-fitting sock or shoe, for example, damages the structural connection between skin layers and separates them. The body responds by building up fluid in the spaces between those layers to protect them from further damage and allow for easier and faster healing.
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The main problem with a blister is not its formation but the risk of rupturing the thin skin layer protecting the wound, also known as the “roof.” Without a roof, your raw skin will be exposed, requiring extra care to prevent infection. Needless to say, a ruptured blister is extremely painful and will surely make the walk or run back to the trailhead or finish line a miserable trek.
Fortunately, blisters don’t start out as massive, painful, fluid-filled bubbles. They typically present first as what Larson calls a hot spot: a small area on your foot that slowly starts to feel sore or sensitive. This means that addressing the issue right away can make your day a lot easier.
How to prevent blisters on feet
As with most health-related issues in the backcountry, when it comes to blisters, prevention is key. This means you’ll need to pay special attention to what you put on your feet.
Sweaty or damp socks and shoes can increase the chances of blisters forming. If your day is likely to include long stretches of walking or running, choose socks made from synthetic, moisture-wicking materials. Cotton and other natural textiles just won’t dry up quickly enough while you’re hiking. Oversized socks don’t help either, as the extra fabric can bunch and rub, creating excessive friction and discomfort.
Likewise, make sure your shoes fit properly. They shouldn’t slip around on your feet when you’re walking but should leave enough room for swelling if you plan to be on your feet for most of the day. If you buy new hiking shoes, the general recommendation is to choose footwear half a size larger than you normally would. You should also break them in by wearing them around town or at home for a few days prior to any big athletic pursuits. The same rule doesn’t necessarily apply to running shoes, so the safest bet is to go to a specialized store and have your feet measured by a salesperson. They’ll be able to guide you through choosing the best shoe size and model for you depending on the distance you plan on covering and the shape of your feet.
Heavy leather boots are usually harder to break in and often more likely to cause blisters, as they’re not as flexible or breathable as other footwear. If you’re hiking or backpacking and are prone to blisters, consider wearing lightweight boots or trail runners instead. If you know there are spots on your feet prone to getting blisters or your shoes feel especially tight in some areas, Larson recommends using kinesiology or waterproof first-aid tape to preemptively cover trouble zones and keep them from becoming a full-blown problem later.
Once you’re ready to hit the trail or pound the pavement, check your socks and shoes for debris. Remove any particles that might grate against your skin by dumping out your boots and turning your socks inside out.
It doesn’t matter how many preventive measures you took: If you feel a hot spot or any sort of discomfort while you’re moving, Larson says you should stop immediately. Take a break and find the source of the irritation. Pay special attention to seams, debris, or loose socks, and remedy or remove the offender, if possible. To protect the spot from future aggravation, cover the damaged skin by slapping on a blister bandage or a piece of kinesiology tape. The latter is Larson’s favorite because it’s breathable, flexible, and sticky enough to stay put for days if necessary.
How to treat blisters
If, despite your best efforts, you still find yourself with a blister, your best bet is to treat it early. Whatever you do, don’t tear or peel away the roof: “You’re just creating a bigger wound with a greater risk of infection,” Larson says.
Dealing with a small blister that is soft to the touch (meaning is not entirely filled with fluid) is easy—just stick a blister bandage or piece of kinesiology tape directly over the offending spot. It should be large enough to extend beyond the boundaries of the blister area.
But if the circumference of the blister is larger than a nickel or is fully filled with fluid and likely to rupture, you’ll need to carefully drain it first. To do so, wash your hands thoroughly and sanitize the skin around the blister with soap and clean drinking water, or an alcohol pad. Next, disinfect a safety pin with a different alcohol pad. If you don’t have one, you can also heat the pin over a lighter until the tip glows red. Just make sure to let the metal cool down before you use it to poke a small hole in the bottom of the fluid-filled bubble. Gently press on the blister to completely drain it out, and place a donut-shaped bandage around the outer edge of the wound or apply an adhesive blister bandage. This will prevent shoes or straps from pressing directly on the sensitive area.
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If the blister has ruptured or the roof is off, you should take special care to prevent infection. Wash your hands and clean the area thoroughly before placing the donut-shaped bandage around the wound, and then cover the area with a large bandage. If it’s really raw, say, if the roof has peeled back and your socks or shoes have been rubbing the wound for some time, use a hydrocolloid bandage. Larson also recommends making a jelly donut: use a moleskin donut bandage and cover the ruptured blister with 2nd Skin Squares, a jelly-like product that protects and moisturizes the skin to stimulate healing. Finish by covering everything up with a piece of kinesiology tape or an adhesive bandage.
With an open wound such as a roofless blister, preventing infection is your first priority, but Larson doesn’t often recommend applying antibiotic ointment. She explains that the cream can attract more dirt and keep bandages from sticking in place.
Tips and tricks for treating blisters
It’s a good idea to keep some blister bandages in your first aid kit, but don’t fret the next time you’re in the backcountry and you find you have none. Larson has used and seen plenty of less conventional blister treatments, from breathable and flexible kinesiology tape to duct tape.
While she doesn’t prefer the latter, it can work in a pinch, especially if you cover the blister with a folded piece of tape (sticky sides together) slightly bigger than the circumference of the wound, and cover everything up with a larger strip. That will keep the adhesive from being in direct contact with delicate and damaged skin.
Larson is a big fan of hydrocolloid bandages, which are available at your local pharmacy. But be wary of traditional adhesive bandages, as they tend to slip off in the presence of sweat and moisture. She also suggests experimenting with different products to see what works for you but recommends you always keep some tape, a couple of alcohol prep pads, and a pin on hand, just in case.