If you've ever finished a long run and dreaded that post-race shower, you already know how chafing can ruin a good run (during or after the fact). That burning, raw feeling on your thighs, under your arms, your chest, or pack straps is one of the most common yet preventable problems in running. Whether you're training for a marathon or just putting in your biggest miles of the week, chafing doesn’t need to slow you down. Running is hard enough, don’t make it harder by dealing with skin irritation.
Here's everything you need to know to stay comfortable from mile one to the finish line.
Why Chafing Happens in the First Place
Chafing is skin damage caused by repeated skin on skin or skin on fabric friction. A short run in good conditions might not cause any issues at all. But add distance, heat, humidity, and sweat, and that same friction becomes a real problem.
Summer makes everything worse. Higher temperatures mean more sweat, and sweat accelerates the breakdown of whatever protection you've put in place. Long summer training runs mean a lot of time on your feet. More time equals more friction, and more friction equals more damage.
Chafing can range from mildly irritating to severe enough to draw blood. Either way, if it happens mid-marathon or mid-long run, it's going to affect your performance and your day.
Where Chafing Hits Hardest
Knowing your problem spots before you head out is half the battle. These are the areas that cause the most trouble on long runs and marathons:
Inner thighs — The most common spot, especially as shorts ride up or fatigue sets in and your gait changes.
Underarms — Repetitive arm swing over long efforts turns even soft fabric into sandpaper by mile 15.
Nipples — Shirts rubbing cause issues. If you've never dealt with this, protect them before you have to.
Sports bra lines — The edges and back clasps are a major source of chafing for women, especially once they're soaked through.
Pack Straps – Your running pack rubbing along your shoulders for 3 hours can cause major issues.
HOW TO PREVENT CHAFING:
Wear the Right Gear
Before you reach for any product, your gear choices make a significant difference.
Ditch the cotton. Cotton holds moisture against your skin. On a short run it's fine. On a two-hour summer long run or a marathon, a soaked cotton shirt becomes one of the most abrasive things you can wear. Stick to moisture-wicking synthetics or merino wool that move sweat away from your skin.
Fit matters more than you think. Gear that's too loose shifts and bunches. Gear that's too tight creates constant pressure points. Make sure everything fits well before your longest training runs, not on race morning.
Use the Right Anti-Chafe Product
Gear helps, but on a long run or marathon, you're going to need a product too. Not all of them are created equal and the difference matters most when the miles get long.
Petroleum based balms create an occlusive barrier on top of the skin that reduces friction. For a 5k or a short ride, they work fine. The problem is that barrier erodes as sweat builds. What was protecting you at mile 5 is gone by mile 13, right when friction is at its worst and your skin is most vulnerable.
Natural anti-chafe balms work differently. Ingredients like coconut oil, cocoa butter, and beeswax moisturize the skin rather than just sitting on top of it. Beeswax holds everything in place through sweat, rain, and whatever conditions you're running in, giving you lasting protection that doesn't break down when the effort gets hard.
Squirrel's Nut Butter was built for exactly this. Four simple ingredients, no synthetic fillers, and a track record that includes 100-mile races, multi-day desert events, and FKTs on the Appalachian Trail. Athletes who know that chafing can end a race don't leave it to chance. They use something proven.
Apply It the Right Way
Even the best product won't help if you're applying it wrong.
Apply to clean skin before you sweat. Anti-chafe balms absorb and adhere best to dry skin. Put it on before you leave the house, not in the parking lot after warming up.
Be generous on high-risk spots. Don't skim the surface on your inner thighs or underarms. Work it into the skin so it has a chance to do its job.
Don't forget your feet. A thin layer between your toes and around the heel collar of your sock can be the difference between finishing strong and limping through the last few miles.
On efforts over three hours, consider carrying a small amount for reapplication. Even the best products can use a refresh in extreme heat and humidity.
Other Tactics Worth Knowing
Tape problem areas. For spots that are especially prone to irritation — nipples, known hot spots — a small piece of athletic or kinesiology tape adds a physical barrier. Just don't combine it with lubricant or it won't stick.
Stay hydrated. This one surprises people. When you're well hydrated, the salt concentration in your sweat is lower. High-salt sweat is more abrasive and dries into crystals on your skin that cause additional friction. Aim for water every 15 to 20 minutes on long efforts.
Be careful with shaving. Freshly shaved skin is more sensitive and more prone to irritation. If you can, avoid shaving the day before a long run or race. If you need to, use an electric trimmer rather than a razor.
Consider thigh bands. If inner thigh chafing is a recurring problem for you regardless of what you apply, a silicone-edged thigh band adds a physical layer of protection that works well alongside a good balm.
The Bottom Line
Chafing is common but it's not inevitable. The right gear, the right product applied the right way, and a little awareness of your problem spots is all it takes to stop it from becoming a factor in your running.
You're putting in the miles. Don't let something this preventable slow you down.
Try Squirrel's Nut Butter on your next long run and feel the difference. [Shop here.]
