Foot Blisters 2
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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Foot Blisters 2

This is the second post based upon educational sessions and syllabus material presented at the Wilderness Medical Society Annual Meeting & 25th Anniversary held in Snowmass, Colorado from July 25-30, 2008. The first post was a discussion of blister formation and prevention, with expert advice from Dr. Grant S. Lipman of Stanford University. Now, we will learn more from Dr. Lipman about blister management:

Treating a blister as soon as possible reduces complications from further tissue damage or infection. As mentioned in the previous post, a sensation of warmth associated with a “hot spot” is a warning sign for an impending blister. Prompt attention and rapid intervention can halt the abrasive process to prevent progressive blister formation. Options for hot spot treatment include the preventive taping/lubricant measures mentioned or more expensive adhesive/gel pads, such as Band-Aid Blister Block or Blist-O-Ban (the latter scientifically proven to generate less friction than less expensive options such as adherent felt or moleskin).

Blisters deep to a callus should not be drained, as this is a painful and difficult process. These sub-callus blisters quickly refill with fluid after drainage, and the process can introduce bacteria that cause infection. Likewise, blood-filled blisters should be left intact, because of a similar concern for infection.

Any blister with murky fluid, that is draining pus, or which is associated with warm, red skin or red streaking towards the heart may be infected. The blister should be drained and have antibiotic ointment applied, and there should be consideration for the addition of an oral antibiotic.

The best protection for a blister is its own roof. Small intact blisters that are not causing significant discomfort should be left intact. To assist in protecting this roof, a small adhesive bandage or pad can be applied. Be certain to place a first layer of paper tape under any adhesive tape, so you do not inadvertently de-roof the blister when removing the tape.

The pain from a blister is due to pressure on the incompressible fluid trapped between skin layers. As the abrasion and pressure builds, there is further weakening and separation of skin layers and increased potential for rupturing the blister. When a blister opens, raw skin is exposed. If a blister is punctured with a needle and drained, it will often refill within a few hours. If a large hole is made that allows continuous fluid drainage, there is risk for tearing off the roof and leaving a large damaged area.

So, there is no one correct way to manage a blister. For every technique and product mentioned, there are at least several different options. The following blister treatments assume that you must continue on your feet, because resting and “staying off your feet” is not an option.

Basic Blister Treatment (for intact blisters):

1) Cut moleskin (or a basic blister care product) into a donut of diameter ½ inch to 1/3 inch around the blister. The blister should fit inside the hole in the donut.
2) Place a patch of Spenco 2nd Skin in the donut hole directly over the blister.
3) Cover the moleskin donut and patch with benzoin and tape.

Note that this “traditional” moleskin/donut treatment may cause further pressure points either directly under the moleskin or by transferring pressure and subsequent increased friction to the opposite side of the foot.

Basic Blister Draining:

1) Cleanse both the blister skin and a safety pin with an alcohol pad (the diameter of a safety pin is larger than that of a sewing needle to allow continuous drainage, yet not so large as to risk de-roofing the blister).
2) Puncture the blister with the pin at several points at the margin of the blister (generally on the outside of the foot), rather than via one large hole. This will allow natural foot pressure to continually squeeze out fluid, limiting the risk of de-roofing the blister.
3) Gently push out fluid with your fingers.
4) Blot away the expressed fluid.
5) Cover the drained blister with paper tape (protects the blister roof when any other overlying tape is removed).
6) Cover the paper tape with benzoin, then with shaped adhesive tape. All tape should have trimmed and rounded edges to minimize “dog ears” and peeling off.
7) Reaccumulated fluid can be drained through an intact bandage.

Open and Torn Blister Treatment:

1) Using small scissors or another sharp object, carefully de-roof the blister, completely trimming off the dead skin.
2) Place Spenco 2nd Skin on raw skin.
3) Cover the Spenco 2nd Skin with paper tape.
4) Apply a benzoin coating.
5) Cover with Elastikon or another tape product.

Toe Blister:

1) Drain the blister with an alcohol-cleansed safety pin.
2) Use one piece of Micropore tape to encircle the (leaving the torn
tape end at the dorsum of the foot to avoid irritating neighboring toes).
3) Pinch closed the tape.
4) Trim sharp edges or wrinkles in the tape. Avoid cloth tape or Elastikon on the toes, as the abrasive nature of these tape varieties may cause blisters on adjacent toes.

Advanced Blister Care Treatments:

1) One may advance a needle and thread through two sides of a blister, leaving ¼ inch of “tied tails.” The thread wicks away moisture and dries quickly. However, leaving an exit source and a wick in the wound may allow entry of bacteria.
2) De-roof the blister, then pour on Mercurichrome. This may be incredibly painful. This therapy is sometimes controversial, because of issues with pain and tissue toxicity.
3) Inject tincture of benzoin or New-Skin liquid bandage directly into the blister. This seals the blister, but may be incredibly painful.

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