Acne Mechanica: Breakouts From Hats, Helmets, Straps and Friction

Acne mechanica is acne triggered by friction, pressure, heat and trapped sweat, usually from gear that sits on the skin: helmets, chin straps, hats, headbands, backpack straps, shoulder pads or tight synthetic clothing. It starts as small rough bumps where the gear touches. The fix is to cut the rubbing with soft, clean padding and moisture-wicking layers, clean your gear, and treat the area with salicylic acid.

The good news is that it usually clears faster than regular acne once you change the setup. Below: how to recognize it, which sports and hobbies cause it where, gear and cleaning fixes that work, how to treat it, and the look-alikes worth knowing about. Breakouts under face masks are their own topic, covered in our guide to maskne.

What is acne mechanica?

It is a form of acne caused by physical stress on the skin. The AAD explains that you get it when sports equipment or clothing traps heat and sweat on your skin and then rubs against it, irritating the skin enough to set off new breakouts in people who are acne-prone. A dermatology case report gives a broader definition: any acne-like eruption in areas of friction, pressure, stretching, rubbing, pinching or occlusion, in anyone, whether or not they already have acne. Reported causes include leaning against a chair or bed for long periods, occlusive clothing and a prosthetic limb.

What does acne mechanica look like?

The first sign, according to the AAD, is small, rough-feeling bumps that you can feel more easily than see, right where a strap, helmet or other gear rubs. If you keep using the gear without changing anything, those bumps can turn into pimples and sometimes deep cysts. The giveaway is the map: the breakouts trace the outline of whatever touches your skin, such as a line along the forehead where a hat band sits or two patches where backpack straps cross the shoulders.

Which gear causes acne mechanica, and where?

Anything that presses and rubs on warm skin can do it. The AAD lists these examples:

Source: the AAD's list of sports equipment that can lead to acne mechanica; the body sites follow from where each item touches.

Can hats and headbands cause forehead acne?

Yes, in two ways. A tight band holds heat and sweat against the forehead and rubs as you move, which is classic acne mechanica. Hats and headbands also collect hair product residue. The AAD notes that oils in shampoos, conditioners and styling products can cause tiny bumps along the hairline and forehead, and that the residue sticks to things your head touches, so it recommends washing caps, hats, headbands and visors along with pillowcases. If you get a band of tiny skin-colored bumps on your forehead, our guide to closed comedones on the forehead explains how to clear them.

Why do backpack straps cause acne?

Straps press on the same strip of skin for hours and slide a little with every step, and the padding under them gets damp with sweat. The AAD advises avoiding anything that rubs against your back, such as a backpack, while you're breaking out: swap to a handheld bag, or carry a shoulder bag with the strap over your arm. If you need the backpack, a padded, well-fitted pack with a sternum strap keeps it from shifting, and a clean, sweat-wicking shirt between the straps and your skin reduces friction.

What is fiddler's neck?

Fiddler's neck is a related friction problem rather than true acne: a skin reaction in violin and viola players where the instrument sits against the neck. A review describes it as common in these players, showing up under the jaw, above the collarbone, or both. The review explains that the patch under the jaw comes from pressure and shear on the skin and can show redness, scarring, swelling and thickened skin, while the patch above the collarbone is usually an allergic contact dermatitis. In one reported case, the allergy was to nickel in the bracket holding the chin rest, and it cleared after a switch to a nickel-free composite chin rest.

Management listed in the review includes a topical steroid, better instrument handling, neck padding, changing the instrument's materials and cutting playing time, and it warns that surgery is usually not advisable. A review of skin disease in musicians adds that repeated physical trauma is a frequent cause and that adjusting playing technique to reduce it is part of prevention. Because fiddler's neck can be mistaken for other neck lumps, have a dermatologist look at any persistent swelling.

How do you prevent acne mechanica?

Reduce friction, heat and grime at the point of contact. The AAD recommends:

• Add a clean, soft layer. Put clean, soft padding between the equipment and your skin to stop the rubbing. A thin cotton or moisture-wicking skull cap under a helmet, or a sweatband you wash after each use, does this job.
• Wear moisture-wicking fabric next to your skin. It pulls sweat away and reduces friction.
• Go looser. Trade tight workout clothes for loose-fitting ones so heat and sweat don't get trapped.
• Start with clean clothes. Put on workout clothes that have been washed since you last wore them.
• Don't share protective gear like helmets and shoulder pads when you can avoid it, and wipe off shared equipment before using it.
• Pat, don't rub. Use a clean towel to gently pat sweat away.
• Shower soon after. If you can't, change out of your gear and wipe breakout-prone skin with salicylic acid pads.

For your own gear, wash removable helmet pads, liners and chin-strap covers often, following the manufacturer's care label, and let them dry fully between sessions. For a full post-exercise routine, see skincare after the gym.

What is the best treatment for acne mechanica?

Salicylic acid is the AAD's first suggestion. It says an acne medication with salicylic acid often works well to clear this type of acne because it helps unclog pores, and you can buy it without a prescription; US over-the-counter acne products may contain 0.5% to 2% salicylic acid. A salicylic acid cleanser or leave-on product over the whole affected area, used daily, is a sensible start. Our guide to salicylic acid covers how to use it without drying your skin.

1. Fix the gear first, using the steps above. Treatment can't outpace daily rubbing.
2. Apply salicylic acid in a thin layer over the whole contact zone, not just the visible bumps; the AAD says spot treating fails to prevent new breakouts.
3. Keep the rest of your routine gentle. Scrubbing and drying skin out can make acne flare.
4. Give it time. The AAD says acne mechanica tends to clear more quickly than regular acne, and if it's still there after six to eight weeks of treatment, see a dermatologist.

A dermatologist may prescribe acne medicine, and the AAD notes that for some patients microdermabrasion or laser therapy can help. If you're pregnant, check with your doctor before starting a new acne product; the AAD says salicylic acid is generally considered safe when used for a limited time but worth discussing first.

Could it be something other than acne mechanica?

A few conditions look similar, and they need different care:

How can an app help you track friction breakouts?

Acne mechanica on the forehead, chin and jawline shows up in a selfie, which makes it easy to track. Pori takes a selfie and returns an overall skin score plus a breakdown that includes Pores & Texture, and its before/after comparison lets you check whether a new helmet liner or headband routine is working. The skin diary logs sleep, water, stress and diet next to each scan, and the ingredient scanner (part of Pro) checks the labels of your face wash, sunscreen and hair products against your skin type. For a photo routine that gives you a fair comparison, see how to track acne progress.

An app is not a diagnosis. It can't tell acne mechanica from contact dermatitis or acne keloidalis nuchae, so see a dermatologist for bumps that hurt, scar, itch badly or don't settle after six to eight weeks.