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Blisters develop from excess friction where the top layer of skin separates from the underlying dermis. The dermis is the white skin seen when an abrasion occurs. The dermal layer of skin has live cells and specialized glands. The top layer or epidermis is protective and without live cells. Over time a callus, an adaptive thickening of the epidermis can occur. Hands and feet are commonly afflicted with blisters.

Direct causes of excess friction and blisters can be from ill-fitting shoes, or simply from a lot of walking or running on any surface. Pivoting the foot in basketball or tennis can bring on a blister under the ball of the foot. Using a tool in your hands repeatedly can cause similar blisters and calluses as seen in the feet.

Indirect causes can be the form or function of the foot. Form is the shape of the foot. For example, a bunion, hammertoe or prominent bone can rub more easily in the shoe. A high arch foot may put more pressure on the heel and ball of the foot.

Function of the foot can affect excess friction. In a flexible hyperpronated foot the toes grab more to compensate and can contribute to blisters at the ends of the toes. A supinate high arched foot might cause more friction on the outside of the heel.


Form and function refer to you, and what God gave you to get around on: the shape of your foot and how it pronates or supinates. You get the idea.


Identifying the causes, means of prevention, and finally, treatments will be covered here.
A “normal” amount of pronation occurs in the foot followed by a normal amount of supination during the “stance” phase of walking when the foot is on the ground. Shoes alone can be the source of blisters.

They can be ill-fitting, made of non-yielding materials or simply have a design flaw. Man made “uppers” are usually synthetic and non-yielding. Leather or canvas shoes can stretch to give room for normal movement of the foot. A design flaw could be the thick stitching in the upper crossing over the toes or other prominent parts of the foot.


Runners soon learn to master self-treatment. This blog will help us compare notes to better prevent those blasted blisters.


As we age…

Just when you think you know how to prevent blisters, for example using duct tape, moleskin or Vaseline on the ball of the foot, a new kind of blister developers at the end of your toes. At least this happened to me, and of course, I should know better.

So let’s start with what happens over time. Your feet increase in shoe size. Gravity flattens the arch some over years; a size 10 and a half in college can be an 11 by 40 years of age and a 13 when in your sixties! Now that might be extreme, but in runners, shoe fit is more critical when banging the ends of the toes. At least it happened in my case where my feet are more on the flat side to start with.

Other orthopedic deformities, form or shape conditions, are seen more as we age. Mild hammertoes become more hammered, bunions enlarge, and we lose the fat under the ball of the foot. In losing the fat pad, a metatarsal bone can be more prominent, dropped, or susceptible to pivoting shear force.

I was so surprised when a local running store jumped me to a size twelve when in my 50’s. More recently,  I mistakingly was using my son’s size 13 when doing a Mainly Marathon series (where runs are done up to seven days in a row). After using his 13’s, on series in the Fall, I went back to my size 12’s for a Mobile, Alabama marathon in January. My feet had caught up with the shoe length, and I suffered from blood blisters at the ends of my great toes. I now regularly wear size 13’s.


If the shoe doesn’t fit don’t wear it…

Recently, a high school runner presented himself to my office with blisters on the outsides of his feet in back of his little toes. He was a big-boned with wide feet. We have a lot of those in the Midwest. While cross country was his thing, shorter track events took place in Spring. And he was using spikes bought online.

To evaluate the correct shoe size, I had the patient stand on a sheet of paper and drew an outline of his foot. Then I placed the shoe with spikes inside the outline, there were almost two inches of extra width in the outline of his forefoot! He had an early Taylor’s bunion, a knot where the small toe joint connects to the foot. This “form” had a little to do with the blisters; most of the cause, however, was the pair of narrow spikes bought online.

So first and foremost, proper shoe fit, preferably at a running shoe store is periodically recommended. It’s best to fit shoes at the end of the day when the feet are slightly larger from swelling.


Functional Issues

My right foot functions poorly. It turns out more flops or hyper-pronates. To help correct this, the long flexor tendons that insert to the end of the toes tend to grab or pull more, to protect the arch. Its fancy name is “flexor [tendon] substitution”. This can still happen, even with orthotics, when first doing your long run or race of ten miles.

I remember it as a ten-mile race that gave me a large blister on the bottom of my fifth toe, and to a lesser extent on the fourth toe. The fifth toe was so injured that there was blood in the blister, a blood blister.

So function, as well as form of your foot, can be indirect causes. To treat this for future long runs, I Vaselined my toes, but I also cut back my insole so that my toes had more room to grab.


Treatment of Blisters

So how do we address blisters? First-aid is, of course, to clean, drain, apply antibiotic and a bandaid.

How we drain the blister is paramount in preventing the blister from re-forming. I believe in the approach that makes a large enough draining hole that won’t reseal, while still leaving most of the skin intact to protect the dermis. One should do this aseptically. I do not burn and sterilize a needle because the resulting hole is not large enough and will re-seal. The dermal cells are alive and have been inflamed; fluid will continue to seep if there is not sufficient drainage.

What has worked for me is to use a pair of scissors to nip a small 1/8″-1/4″ hole in the blister. This usually prevents resealing of the blister. Of course, the scissors are clean and wiped with alcohol for good measure. Again, the blister is covered with antibiotic ointment and a band-aid or a second skin product such as the ones developed by Spenco.



As mentioned above, vaseline is my first choice in the prevention of blisters. Regular foot or talcum powder works well in triathletes. The shoes are powdered ahead of time. I use orthotics of ¾ length so my toes have plenty of room. This length also can be cut just behind the ball of the foot to effectively lift the ball of the foot more, minimizing friction blisters there. When one does a street marathon like Chicago, the Street-effect is like repeated slapping of the forefoot. The ¾ length insole rise helps keep the feet cool.

Second Skin products, first done by Spenco, help when you are still recovering from a relatively new blister. I have used these band-aids like covers with impregnated gel on the ends of my great toes and on the ball of the foot. Straight moleskin applied to a day old blister works for many. Moleskin is a thin felt product with an adhesive backing. You then cut the pad to cover the affected area. Duct tape has been used preventively, but again I preferred vaseline.

Spenco insoles were originally designed to prevent blisters on the balls of the feet when playing tennis. Consider the shear force. The green cover is on a neoprene rubber with injected air bubbles that help absorb the sideway or shear friction force. Dr. Spencer, behind the Spenco name, liked to play tennis.

Double layered socks help with blister prevention. Avoid cotton as it absorbs moisture, may clump and cause a blister. Most socks made for runners are of synthetic materials. The support stockings are popular these days. They come either toe to knee, or ankle to knee and can vary in pressure from mild (15-20 mmHg) to fairly tight (40-60 mmHg).

With the tight support full-length stocking, it can be a disaster if you get a blister on the foot halfway through a marathon. The calve-only length will allow you access to a burn spot or early blister to Vaseline if necessary. Often Vaseline is available in the latter half of a marathon at the aid stations.


Pressure on hammertoes can be eliminated with a wider and deeper toe box, such as the one seen in Altra shoes. In addition, a neutral or negative heel lift can help offload the ball of the foot and blisters that occur there.

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