Acne mechanica: backpacks, straps and tight clothes

A backpack, a sports bra, a helmet strap, a weight bench and a pair of tight leggings have one thing in common: they press and rub on the same patch of skin for hours, and they hold heat and sweat there. When acne appears in exactly that patch, doctors call it acne mechanica. The name comes from "mechanical," because rubbing and pressure cause it. This guide explains how it forms, how to recognize it, how to treat it, and how to keep doing your sport or carrying your bag without it. It is part of Skinli's guide to body acne.

Skinli gives general education, and it is not a doctor. Deep or painful lumps need a dermatologist.

How acne mechanica forms

The American Academy of Dermatology (AAD) says "you get this type of acne when sports equipment or clothing traps heat and sweat on your skin. As the equipment or clothing rubs against your heated skin, your skin becomes irritated. If you have acne or acne-prone skin, this irritation can cause new acne breakouts."

A 2026 review of acne on the chest, back and shoulders traces the term to two dermatologists, Mills and Kligman, in 1975. It describes acne mechanica as acne caused by "friction, pressure, traction, tight clothing, or occupation-related rubbing," and says long hours under clothing create a warm, damp layer that can add to the swelling. The review also says acne on the trunk "may be more strongly influenced by mechanical factors" than acne on the face.

NIAMS, part of the US National Institutes of Health, lists "pressure from sports helmets, tight clothes, or backpacks" among the things that can make acne worse.

Common sources

The AAD lists gear that can cause acne mechanica. Here it is grouped by where it touches the body:

Area	Sources the AAD names
Back and shoulders	Backpacks, especially the straps; football and lacrosse shoulder pads; golf bag straps; the back of a racing driver's seat
Chest	Hockey chest protectors
Head, chin and neck	Helmets, chin straps, wrestling face guards, a shot cradled against the neck
Whole trunk	Synthetic dance and gymnastics clothes
Back and waist	Plastic weightlifting benches and weightlifting belts

Everyday items work the same way, including bag straps that rest on the shoulders (see shoulder acne). The AAD's back acne page says "anything that rubs against your back, such as a backpack," can make back acne flare, and suggests carrying a purse with the strap on your arm. Its pages on bumps at the back of the neck list shirt collars, chains and hats. The AAD also says tight clothing can damage hair follicles and cause folliculitis, which looks like acne.

A 2025 survey of 602 gym users in Saudi Arabia found that among the 200 who said exercise irritated their skin, 25% reported acne mechanica.

How to recognize it

The AAD describes the first sign as "small, rough-feeling bumps that you can feel more easily than see." They appear where a chin strap, helmet or other gear rubs. If you keep using the gear without changes, "these small, rough bumps can turn into pimples and sometimes deep acne cysts."

Clues that point to acne mechanica:

• The bumps sit under a strap, pad, band or seam, and the patch has the same shape.
• They started after you took up a sport, a hiking trip, a heavy bag or a work uniform that sits on that spot.

Rough bumps that stay the same all year on the upper arms and thighs are more likely keratosis pilaris. See acne on arms and thighs. Itchy bumps that all look alike may be fungal acne.

How to treat it

The AAD says it is possible to keep playing your sport and see clearer skin. Its advice:

1. Pad the gear. "Place clean, soft padding between the equipment and your skin." This can remove the rubbing.
2. Wear moisture-wicking fabric next to the skin. The AAD says it "pulls sweat away from your body, reducing the friction."
3. Trade tight clothes for loose ones. This "helps prevent heat and sweat from getting trapped on your skin."
4. Use salicylic acid. The AAD says "using an acne medication with salicylic acid often works well to clear this type of acne," because it helps unclog pores. It is sold without a prescription. A body acne spray or acne body wash can reach the back.

The AAD says acne mechanica "tends to clear more quickly than regular acne." If it is still there after 6 to 8 weeks of treatment, a dermatologist can help, and a prescription medicine may be needed. For some patients, the AAD says, microdermabrasion or laser therapy can help.

An 8-week plan

When	What to do	Source
Day 1	Find the strap, pad, seam or tight item on that spot, and pad it, loosen it or stop using it	AAD sports gear page
Days 1 to 3	Try the salicylic acid product on one or two small areas first	FDA acne label rule, optional sensitivity test
First 2 weeks	Use it once a day on the whole area that breaks out	FDA acne label rule
After that	Go up to two or three times a day only if needed, and back to once a day or every other day if skin gets dry or peels	FDA acne label rule
Weeks 6 to 8	Judge the result. If the bumps remain, see a dermatologist	AAD sports gear page

The FDA requires every acne label to warn that irritation "is more likely to occur if you use another topical acne medication at the same time," so start with one product.

Acne mechanica or folliculitis?

Tight clothes and heat can cause a second problem that looks like acne. The AAD says folliculitis, an infection of the hair follicles, starts when follicles are damaged by "wearing tight clothing," "having skin rub against skin" or shaving, and that "when your skin is damp and hot, it's easier to damage your hair follicles and get an infection." Its example is tight clothing rubbing during a bike ride on a hot day.

Clue	Acne mechanica	Folliculitis
First sign	Small, rough bumps you feel more than see	Sudden spots that look like an acne breakout
Each spot	Grows into a pimple if rubbing continues	Often has a red ring around it
Feeling	Rough to the touch	May itch, hurt or cause no feeling
What helps	Padding, loose clothes, salicylic acid	Stopping the cause, warm compresses, sometimes an antibiotic from a doctor

Body acne or folliculitis explains the difference in more depth.

Work uniforms and helmets

The 2026 review includes "occupation-related rubbing" in its description of acne mechanica. The AAD's pages on bumps at the back of the neck say a hard hat, helmet, cap or collar can irritate the skin there, and suggest collarless shirts and hats that stop short of the bumps. If your job requires a helmet, harness, tool belt or stiff uniform, the same padding and loose-fit advice applies wherever it presses.

Backpacks and bags

A bag rubs the same spot every day. What the AAD suggests:

• Swap a backpack for a handheld bag when you can.
• Carry a shoulder bag with the strap on your arm.
• When you do use a backpack, the padding advice above applies to its straps too.

Tight clothes, bras and leggings

Tight tops, sports bras and leggings press on the chest, back, buttocks and thighs. The NHS advises people with acne on the body to "wear loose, breathable clothing (especially when exercising or sweating)." The AAD's workout page adds:

• Put on workout clothes that have been washed since you last wore them.
• Change out of sweaty clothes soon after exercise, and shower if you can.
• If you cannot shower, wipe the skin that breaks out with a salicylic acid pad.

For some people, tight clothing is part of a different condition. The AAD says people with hidradenitis suppurativa, which causes deep, painful lumps where skin touches skin, should wear looser clothing if tight clothes make their lumps flare.

Keep shared gear clean

The AAD says acne is not contagious. It also says shared helmets and shoulder pads "can be full of acne-causing bacteria and oil." It suggests avoiding shared protective equipment whenever possible and wiping off shared equipment before you use it.

What to avoid

• Picking and popping. The AAD says popping at home often pushes what is inside a pimple deeper into the skin, which increases inflammation and can cause scars.
• Scrubbing. The AAD says scrubbing irritates skin and can make acne flare. Rubbing is the cause of acne mechanica, so more rubbing makes it worse.
• Rubbing sweat off. Pat it off with a clean towel instead.

When to see a doctor

See a dermatologist if:

• The bumps have turned into deep, painful lumps or cysts.
• They are still there after 6 to 8 weeks of treatment and changes to your gear.
• They itch, spread fast, or appeared after a hot tub, which can point to folliculitis. See body acne or folliculitis.

Skinli's free acne plan builds a routine for acne on the face from a photo. For the back, the back acne guide covers a full routine.