How to Prevent Chafing During Long Runs and Workouts

Quick answer

Chafing happens when skin rubs against skin, a seam, or damp fabric for long enough that friction outpaces your skin's ability to recover. Fix the three inputs in order: remove the seam or ridge causing the rub, keep the area dry with moisture-wicking fabric, and reduce friction with a smooth barrier. If you're still raw after changing all three, the garment's cut is wrong for your body, not your skin.

You don't notice chafing starting. You notice it at kilometre eight, when a small hot spot under your arm or along your inner thigh turns into a sharp sting that changes your stride. By the time you're home, it's a raw patch that stings in the shower for three days.

Most advice stops at "use anti-chafe balm." That's one input out of three. Balm helps, but it can't fix a seam that sits exactly where your arm swings or a waistband that rolls and rubs. This guide separates the symptom from the cause so you can fix the right thing, and tells you when to stop patching and change the garment.

Diagnose first: where and when does it start?

Where the chafe appears tells you what's causing it. Inner thighs usually mean skin-on-skin friction, which gets worse with heat, sweat, and shorts that ride up. Under the arms or along the bra band usually means a seam, strap edge, or fabric fold is sitting in a high-movement zone. Nipples, waistbands, and hems point to fabric texture or a loose fit that shifts with every stride.

When it starts matters too. If it flares within the first two kilometres, the cause is almost always a seam or edge in the wrong place. If it only appears past the hour mark, moisture and salt build-up are the bigger culprits. That distinction decides whether you change the garment or change how you manage sweat.

• Chafe in the first 10 minutes: suspect a seam, tag, or strap edge.
• Chafe after 60 minutes: suspect moisture, salt, and fabric saturation.
• Chafe only on hot days: suspect fit that loosens when wet.

Fix the friction source: seams, edges, and fit

A seam that sits in a movement zone will rub no matter how soft it is. Look for flatlock or bonded seams in high-friction areas, and avoid raised side seams on shorts or leggings if your thighs touch. Seamless activewear reduces chafing because there's no ridge to catch skin, but seamless doesn't mean friction-free: a seamless bralette with a snug cross-back strap can still rub if the band rolls.

Fit is the other half. Shorts that are too loose ride up and bunch; shorts that are too tight crease into the hip and groin. The fix is a secure waistband that stays put without digging, and a leg opening that sits flat rather than gripping. If you can pinch more than a centimetre of fabric at the leg hem, it will move. If the waistband leaves a red mark after 20 minutes, it's too tight.

• Choose flat or bonded seams in the inner thigh and underarm zones.
• Test fit by squatting and taking five strides before you commit to a long run.
• Wash new kit once before a long effort to soften any sizing or finish.

Manage moisture: fabric, layers, and timing

Wet skin is weaker skin. Sweat and salt increase friction and soften the outer layer of your skin, so the same seam that's fine for a 5K can shred you at 25K. Lightweight, breathable active fabric moves moisture away from the skin instead of holding it against you. That's why a thin, quick-drying short outperforms a heavier cotton-blend short on long efforts, even if the heavier one feels softer at the start.

Layer smart in the cold. A jacket or long sleeve that traps sweat against your ribs will cause chafe under the arms even if the base layer is fine. If you're running in the rain, expect chafe risk to rise: wet fabric against wet skin is the worst combination. Carry a small amount of balm and reapply at the halfway point rather than only before you start.

• Avoid cotton next to skin on any effort over 30 minutes.
• Reapply anti-chafe balm at the midpoint of long runs, not just at the start.
• Change out of wet kit promptly after training to let skin recover.

Use a barrier correctly (and know its limits)

Anti-chafe balm, cream, or stick works by creating a low-friction layer between skin and fabric. Apply it to skin, not to the garment, and apply more than you think you need on known hot spots. Powders help in dry heat but turn into grit once you sweat heavily, which can make chafe worse. If you're between products, a simple petroleum-free balm is the safest default for long runs.

The limit is simple: a barrier buys you time, it doesn't change geometry. If a seam sits exactly where your arm swings, balm delays the sting but doesn't remove it. If you're reapplying every 20 minutes and still chafing, stop treating the skin and change the garment.

• Apply balm to skin at least 10 minutes before you start.
• Skip powder for long, sweaty efforts; it clumps.
• If balm only works for 20 minutes, the garment is the problem.

Chafe diagnosis: match the symptom to the fix

• Inner thigh rub, starts within 10 minutes: Skin-on-skin friction, usually made worse by shorts that ride up. Switch to a short with an internal brief or a longer, secure leg opening, and apply balm before you start. If it still starts in 10 minutes, the leg opening is too loose. Size down or change the cut.
• Underarm or bra-band rub, any distance: A seam, strap edge, or rolled band is sitting in a high-movement zone. Move to seamless construction with flat or bonded edges, and check the band doesn't roll when you raise your arms. If the band rolls within 20 minutes, the size or support level is wrong, not the fabric.
• Chafe only after 60+ minutes: Moisture and salt build-up. Use quick-drying fabric, avoid cotton next to skin, and reapply balm at the halfway point instead of only at the start. If reapplying every 20 minutes still fails, stop patching and change the garment geometry.
• Waistband or hem rub, hot days only: Fit that loosens when wet. A drawcord or lined waistband holds position better than a simple elastic band. Test by soaking the short and running 5 minutes. If it moves when wet, it will chafe on race day. Choose a different waistband design.

Gear that reduces chafe risk

• Compete 3" Run Shorts - Pacific: Made from lightweight active fabric with a breathable internal mesh brief, invisible zippered side pockets, a back pocket for a phone, and a double waistband design. The internal brief removes skin-on-skin friction between the thighs, and the double waistband is less likely to roll and rub than a single thin band. The zip pockets let you carry balm or a key without adding a bouncing pouch that shifts and chafes.
• Streamline Training 3" Shorts - Tornado: 3-inch inseam, breathable running poly fabric, side splits for mobility, an encased elastic waistband with drawcords, and an invisible zip pocket. Side splits reduce fabric bunching at the hip, which is a common chafe trigger on shorter runs. The drawcord waistband lets you dial in a secure fit so the short doesn't ride up and crease into the groin.
• Sculpt Seamless Bralette - Merlot: Seamless fabric with light everyday support, an open back, and secure cross-back straps. Fewer seams under the arm and along the ribcage means fewer edges to rub. It's a light-support option, so it suits walking, yoga, and easy runs rather than high-impact training where you need a firmer hold.
• Aura Back Pocket Ankle Length Leggings - Black: Aura Fabric with a smooth no front seam design, an MN Essential lined waistband, and a hidden back pocket for a phone, card, or key. The no front seam design removes the seam that most commonly chafes on long runs and rides. The lined waistband stays in place without rolling, which prevents the waistband rub that shows up late in a long effort.

Chafing is a fit-and-fabric problem before it's a skin problem. Diagnose where and when it starts, remove the seam or movement causing it, keep the area dry, and use a barrier as support rather than a cure. If you've fixed all three and it still happens, the garment is wrong for your body. Change it and stop paying in raw skin.