How to avoid blisters when running and trail running?

For regular runners, whether amateur or experienced, few problems are as common and debilitating as a blister on the foot . Whether you're trail running or road running, these small skin lesions can turn a pleasant outing into a real ordeal...

It must be said that foot blisters affect everyone: from the occasional jogger to the marathon runner, including those who enjoy long mountain outings. Understanding their origin, knowing how to prevent them and, if necessary, how to treat them, is therefore essential for any running enthusiast. In this article, we give you tips and tricks to avoid blisters during your running and trail outings .

What is a blister and why does it appear when running?

A blister is a clear fluid-filled blister that forms when the skin is subjected to repeated friction. In running, this friction most often results from contact between the skin, sock, and shoe. With each stride, the foot slides slightly, which heats the epidermis and causes the surface layers of the skin to peel off. The body reacts by producing fluid to protect the injured area.

In both running and trail running, the risk is increased by several factors: uneven terrain, technical descents that cause the foot to move backward in the shoe, perspiration that softens the skin, or even poor equipment fit. The result: blisters on the heel or sole of the foot can occur, as these are areas where excessive pressure is exerted.

Preventing Blisters: The Runner's Golden Rule

While it's possible to treat a blister, the best strategy is to avoid them. Whether you're running or trail running, prevention relies on three key factors: choosing the right shoes, choosing the right socks, and preparing your feet.

Choosing the right shoes

Poorly fitting shoes are the first risk factor:

• Too small, it compresses the foot and increases friction, quickly causing a blister on the toes.
• Too big, it lets the foot slide inside, which leads to chafing on the heel or sole.

Choosing the right size is therefore essential: the shoe must fit the foot without compressing it, while leaving a slight space in front of the toes to absorb shocks, especially when going downhill on a trail.

The Importance of Proper Lacing

Lacing also plays a major role. Lacing that is too loose encourages unwanted foot movement, while lacing that is too tight can create painful compression zones. Ideally, you should adopt a progressive lacing, firm at the instep but more flexible towards the front, to hold the foot without crushing it.

Selecting the right socks

Many runners underestimate the importance of socks. Yet, they're the ones in direct contact with the skin and absorb a large portion of the friction. A poorly chosen sock can turn your run into torture, while a well-fitting pair can be a valuable ally in preventing blisters while running.

Size and fit

The size and fit must be accurate. Quality brands offer socks cut every two numbers, such as 40-41 or 42-43, which ensures an optimal fit.

Conversely, the models covering four different sizes slide or compress according to body shapes...

The materials

The materials is just as essential. Breathable fibers, such as merino wool, modal, or certain technical fibers, wick away moisture better and keep the foot dry, reducing the risk of maceration and overheating.

The design

The design of the sock can also make all the difference. Modern models are seamless at the toe, eliminating painful excess thickness.

• The hemispherical heels, knitted in a Y shape, perfectly fit the shape of the foot and prevent the sock from slipping.
• Some manufacturers differentiate between the left and right foot, ensuring an optimal anatomical fit.
• Finally, the presence of support bands or compression zones ensures that the sock stays in place during exercise.

What about double-skin socks to prevent blisters?

A word about double-skin socks: they significantly reduce friction , since one layer moves with the foot and a second with the shoe. This limits the formation of blisters, but has one drawback.

Indeed, their extra thickness can reduce the feeling of precision and pose a compression problem if the shoe is already fitted. Some runners therefore prefer high-end models, with excellent support, with a single skin. Thanks to a set of compression bands and an anatomical design (differentiated left and right foot and hemispherical heel), a high-end sock can protect naturally, without adding bulk.

Prepare your feet before exercise

Even with the best equipment, an unprepared foot remains vulnerable. Several simple steps can significantly reduce the risk.

Applying talcum powder, for example, absorbs excess moisture and limits perspiration.

Additionally, specific dressings such as anti-blister strips can be placed preventively on sensitive areas, such as the heel or the sole of the foot.

Finally, progressive training also plays a major role. Gradually increasing distances encourages the natural formation of protective calluses. These thickened skin layers, when well distributed, act as a barrier against repeated friction.

What to do when a blister appears despite everything?

Despite all precautions, blisters can still form. In this case, the course of action depends on the size and pain.

A small, painless blister can often be left intact: the fluid it contains protects the underlying skin.

On the other hand, a larger or more painful blister may require a sterile puncture to drain the fluid while preserving the protective skin.

It is important to disinfect the area and protect it with a specific dressing.

Resuming running immediately is not recommended. Of course, during competitions, the urgency often requires managing discomfort in the moment while continuing to race.

To properly treat a running blister, you need to give it time to heal, avoid piercing the skin without strict hygiene, and protect the area during future training sessions.

In short, blisters are one of the classic problems for runners, but they are not inevitable. Understanding why they appear allows you to put the right reflexes in place: choosing suitable shoes, opting for quality socks, preparing your feet carefully, gradually increasing your distances , etc. Thanks to these precautions, it is possible to prevent blisters when trail running and running and to fully enjoy each outing, whether it is a simple race in the city or an ultra-trail in the mountains.