The arch-nemesis of trail runners, blisters are not to be taken lightly. They are the most common running injury and a primary cause of DNFs. While they can often be managed with a few tricks, prevention remains your best weapon. Cimalp explains how to prevent and treat blisters in trail running.
Key takeaways:
- Blisters during trail running are mainly caused by excessive friction.
- To minimise risks, preparing your feet well before race day is essential.
- Technical socks and well-fitted shoes are indispensable.
- Anti-chafing creams and preventive dressings help minimise the risks.
- If a blister appears, prompt action is essential to keep it from worsening.
Why do blisters form on feet?
A blister, or friction vesicle, is a small fluid-filled pocket that forms under damaged skin. To protect the area, the blister rises to the surface, causing pain upon contact or while walking.
In trail running, most foot blisters develop from repeated friction between skin, socks, and shoes. Their formation is further accelerated by moisture, heat, and long-duration efforts.
Several factors cause this friction. First, unsuitable socks: poor fit, wrinkles, or moisture retention will quickly lead to blisters. Second, shoes that are too tight or too loose create unwanted friction points. Finally, skin condition matters: excessively wet or dry feet, as well as poorly trimmed nails, increase blister risk.
How to prevent blisters in trail running?
Prevention is the most effective way to avoid blisters. The first step is to prepare your feet: regular training naturally toughens the skin. Adequate hydration and skin care are equally critical: apply an anti-chafing cream (like Akileïne Nok) in the weeks leading up to the event. Finally, use a foot file or pumice stone to keep calluses under control.
Choosing the right trail socks is crucial. Opt for technical socks made of synthetic fibres or merino wool: they wick moisture, limit friction, and prevent bunching. Choose reinforced socks with extra padding on high-wear zones. You can also try double-layer or toe socks for added protection.
Your trail shoes also play a key role in blister prevention. Choosing the right size is essential: they should secure your foot without pinching. A standard rule of thumb is leaving a finger's width behind the heel. Choose a model adapted to your foot shape with optimal breathability. A breathable mesh helps keep heat and moisture under control.
During a race, take extra precautions to avoid blisters. Trim your toenails the day before to prevent trauma. Before the start, apply an anti-chafing cream and place protective tape or blister plasters (Compeed, strapping tape) over vulnerable zones. During the race, take the time to change socks if they get soaked.
How to treat a blister?
Treating a blister depends on its stage and severity. Act as soon as you feel a hot spot. If the blister is small and intact, protect it with a blister plaster (like Compeed) to prevent further friction.
If the blister is painful, it is best to drain it quickly. Wash your hands and use a sterilised needle. Pierce the edge of the blister carefully and let the fluid drain out without removing the overlying skin. Disinfect with an antiseptic and cover the wound with a sterile, non-compressive dressing.
Post-race, treat your blisters properly to avoid complications. Disinfect them thoroughly and let them air dry if they are unopened. If they are torn, cover them with a sterile plaster and change it regularly. Keep an eye on healing and consult a doctor if you notice signs of infection (severe pain, redness, heat, or pus).
Blisters are not inevitable in trail running. With proper foot preparation, the right gear, and a few basic habits, you can keep them at bay. Look after your feet during training, address any hot spots immediately, and don't delay treatment. You will maximise your chances of crossing the finish line in prime condition.
