Blister: Causes and Treatments | Outdoor and Hiking Safety
Medicine for the Outdoors
Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Blisters: The Bane of Hikers

Blisters are the bane of hikers. These clear fluid- or blood-filled vesicles have probably ended more outings than all major illnesses combined. They can be prevented by keeping feet dry, wearing adequate and properly fitting socks, wearing thin liner socks (polypropylene or polyester) under heavier wool-blend hiking socks, breaking in footgear prior to the expedition, and padding all rough edges within hiking boots. If an area is known to rub, prevent a blister by applying a nonwrinkled layer of moleskin, Molefoam, or athletic tape over the skin before a “hot spot” develops. A terrific method to prevent a potential hot spot (e.g., area that will be rubbed, such as one's heel within a boot) or cover a non-blistered (prior to the appearance of a blister) hot spot is the Blist-O-Ban "bandage" from SAM Medical Products.

If a blister is caused by pressure (ill-fitting boots), you have a couple of choices. As mentioned above, prior to actual blister formation, you can protect or pad the area. Once a blister forms, the blister site can be padded with moleskin or other adhesive foam, so that rubbing no longer occurs, the blister should be ringed with a doughnut of padding and left intact. For a better cushion, a piece of Spenco 2nd Skin (an inert gel consisting of polyethylene oxide and water) can be laid into the doughnut hole and the entire area covered with a second layer of moleskin or an absorbent bandage, such as a Spenco adhesive knit bandage. If no such padding is available, if continued rubbing will rupture the blister, or if the blister interferes with walking, then you can drain it of fluid by using a “sterile” needle (heat a sewing needle to red hot and allow it to cool) to punch a small hole at its edge. If an antiseptic ointment, such as mupirocin or bacitracin, is available, it should be applied to the open wound underneath a sterile (or clean, if "sterile" is not available) dressing or bandage. If the blister appears infected, it should be unroofed entirely, an appropriate dressing and ointment applied, and the victim treated with dicloxacillin, erythromycin, or cephalexin for 5 days or until the skin appears normal. If the dressing (such as Curad Hydro Heal) keeps the blister slightly moist, it may be less prone to drying out and cracking.

Blisters or reddened skin may also be caused by an allergic (“contact”) reaction to chemicals such as formaldehyde or rubber. If a rash is confined to the soles of the feet (shoe inserts) or top of the feet (shoe tongue dye), suspect this problem. In this case, the footgear must be changed.

If a blister is caused by a thermal burn, it should be immediately immersed in cool or cold water (do not apply ice directly to the burn) for 10 to 15 minutes, in order to relieve pain and lessen the ultimate injury. Then dry the wound and apply a soft, sterile dressing. Unless there is a reason to suspect infection (cloudy fluid or pus, fever, redness and swelling beyond the blister edges, swollen lymph glands), burn blisters should be left intact. Opening an uninfected blister or sticking a needle into it risks introducing bacteria that can cause an infection. A topical antibacterial cream, such as silver sulfadiazine or mupirocin, or ointment such as mupirocin or bacitracin, should be applied if the blister is broken, or to prevent the dressing from sticking to the wound. Alternatively, apply a layer of Spenco 2nd Skin or Aquaphor gauze underneath a sterile gauze dressing.

photo of reddened foot courtesy of

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Tags: Backpacking

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About the Author

Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.