Blisters are the most common skin injury in running. In a study of the London and Singapore marathons, 46% of London runners and 36% of Singapore runners developed blisters during the race. If you run long enough, you will get one. But most running blisters are preventable, and the runners who rarely deal with them have usually made the same set of decisions consistently.
What is actually happening
A blister forms when repetitive shear forces separate the layers of skin, creating a gap that fills with fluid. The feet are the most common site, particularly the toes and heels, but blisters can form anywhere footwear or socks create repeated friction against skin. The three drivers are moisture, friction, and fit. Wet skin is softer and more susceptible to shear. Sweat accumulation inside a shoe increases friction between sock and skin. Salt left behind as sweat evaporates adds an abrasive load. Poor footwear fit concentrates pressure into specific hotspots.
Understanding those drivers makes the prevention approach straightforward.
Footwear fit
Footwear fit is the most important variable. Get fitted properly at a specialist running retailer, not a general sports store, and ensure there is enough volume in the toe box for the foot to spread naturally during a run. Toes that are compressed against each other or against the front of the shoe are in a high-friction environment from kilometre one.
The right time to assess fit is late in the day when the foot is at its largest, and ideally after a run when the foot has swollen to its training size. A shoe that fits well in the morning on fresh feet may be too tight by kilometre 20 of a long run.
New shoes should always be broken in gradually. Training the foot and the shoe to each other over shorter distances before committing to long runs reduces the risk of concentrated friction in spots where the shoe has not yet conformed to the foot.
Socks
Socks are the second most important decision and cotton is consistently the wrong answer. Research shows that synthetic or acrylic-blend socks outperform cotton for blister prevention because they move moisture away from the skin rather than holding it against the surface. Wet cotton against the foot during a run is a reliable blister generator. Double-layer socks, which allow the two layers to move against each other rather than transferring shear to the skin, are worth trying for runners who blister frequently despite other preventive measures.
Fit matters for socks as well as shoes. A sock that bunches, slides, or creates seam pressure in the toe box is introducing friction independently of the shoe.
Anti-friction balm
Apply an anti-friction balm to the feet before longer runs and any time conditions will be wet, whether from rain, humidity, or a course with water crossings. The key areas are between the toes, around the heel, and across the ball of the foot. Apply before you start running, before any friction has begun to degrade the skin surface, and be generous.
Do not wait until a hotspot is developing to apply it. By that point the skin surface has already been compromised and the balm is managing a problem rather than preventing one.
For areas that have given you trouble before, paper tape or a blister prevention patch applied over the anti-friction balm adds another layer of protection on longer efforts. The tape reduces shear by giving the friction a surface to act on that is not the skin itself.
Managing wet conditions
Wet conditions significantly increase blister risk because moisture softens the skin and reduces its resistance to shear. Trail runners who regularly run through water crossings, and road runners caught in rain, face a substantially higher blister load than runners in dry conditions.
In wet conditions, apply anti-friction balm more generously and extend coverage to areas that do not usually cause problems in dry conditions. Consider gaiters to reduce water ingress through the shoe collar. Change socks if possible during ultras or very long efforts in sustained wet conditions, as a dry sock on an already wet foot still provides meaningfully more protection than a saturated one.
Managing blisters when they develop
A small, intact blister is best left alone. Clean the area, apply antiseptic, and cover it with a blister bandage. If it is large or in a location that makes running painful, draining it with a sterile needle at the edge is reasonable, but keep the roof of the blister intact as a natural dressing and cover it immediately after.
Never ignore broken skin. Clean any open blister thoroughly, apply antiseptic, and keep it covered during subsequent training. An infected blister can escalate quickly and cost weeks of training. Any blister that is red, warm, spreading, or producing cloudy fluid warrants medical assessment rather than self-management.
Premax Anti Friction Balm is formulated for endurance athletes to reduce friction at the skin surface without blocking sweat glands or interfering with thermoregulation. Apply to the feet and other high-risk areas before every long run.
