Does sweat cause acne? Sweat and body acne

Many people notice more spots on their chest, back or shoulders after they start going to the gym, playing a sport or working through a hot summer. Many people blame sweat. The research gives a more careful answer. Sweat on its own seems to matter less than what happens with it: sweat trapped under tight clothes, gear that rubs, workout clothes worn twice, and towels rubbed hard across the skin. This guide sets out what the studies show, which bumps after exercise are something other than acne, and the habits that help. It is part of Skinli's guide to body acne.

Skinli gives general education, and it is not a doctor. Bumps that itch, spread or hurt deserve a doctor's look.

What the research says about sweat

The American Academy of Dermatology (AAD) says working out "can cause excessive sweating, as well as a buildup of oil, dirt, and bacteria on your skin," all of which can lead to acne. NIAMS, part of the US National Institutes of Health, lists high humidity among the things that can make acne worse, and the NHS advises people with acne on the body to "wear loose, breathable clothing (especially when exercising or sweating)."

Only one trial Skinli found tested sweat directly. In 2008, researchers in the United States asked 23 physically active men to exercise until they sweated, 5 days a week for 2 weeks, and checked acne on the chest and back:

Group	Number of men	What they did
1	7	Did not exercise
2	8	Exercised and showered within 1 hour
3	8	Exercised and waited at least 4 hours to shower

At the end, the researchers found no statistically clear difference in acne between the groups, or within any group from start to finish. The trial was small and short, and a 2026 review of acne on the trunk says its results "should be interpreted with caution." The review reads it as a sign that sweat and exercise by themselves "may have limited impact" on acne on the trunk.

The same 2026 review describes why trapped sweat can still matter. Sweat that collects under clothing "may create a warm and humid microenvironment that may promote mechanical acne and fungal colonization," meaning acne from rubbing and the growth of yeast on the skin.

Where sweat collects on the body

The face has more sweat glands per patch of skin than the trunk. The 2026 review puts the numbers at 270 glands per square centimeter on the face against 160 on the trunk. The trunk makes up for it in size, and much of it sits under clothing all day. The review says sweat can collect under clothing there and form a warm, damp layer against the skin, held in place by a shirt, a bra band or a backpack.

The review also says trunk skin has a thicker outer layer and fewer oil glands than the face, and that acne there "may be more strongly influenced by mechanical factors," meaning pressure and rubbing. For body acne, that points to trapped sweat and rubbing as the parts to manage.

Hot weather and hot jobs

Heat adds to the problem. NIAMS names high humidity as something that can make acne worse. The 2025 review of fungal acne says the yeast infection is more common in people who live in hot climates, "likely due to excessive sweating." In one study it cites, of 48 people with confirmed fungal acne, 83% worked in a warm place and 71% said sweating made it worse. If your bumps flare every summer or at a hot job, that pattern is worth telling a doctor.

Sweat plus rubbing: acne mechanica

The AAD's name for acne caused by gear and clothing is acne mechanica. It forms "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." The first sign, the AAD says, is "small, rough-feeling bumps that you can feel more easily than see," which can turn into pimples and sometimes deep cysts if the rubbing continues.

A 2025 survey of 602 gym users in Saudi Arabia found that 33.2% said exercise irritated their skin. Among those 200 people, 25% reported acne mechanica. The survey relied on what people told interviewers, so it shows how common the complaint is and cannot prove cause.

For more on straps, pads and tight clothes, see acne from backpacks and tight clothes, and for acne where straps and pads sit, see shoulder acne.

Other bumps after exercise

Three other conditions show up after sweating and are easy to confuse with acne:

• Heat rash. The NHS says heat rash "is usually caused by sweating a lot. Sweat glands get blocked and the trapped sweat leads to a rash developing a few days later." It causes small raised spots 2 to 4 millimeters across, an itchy, prickly feeling and mild swelling. The main treatment is to keep cool: loose cotton clothing, light bedding and cool showers. The NHS says it usually gets better on its own after a few days.
• Fungal acne. A 2025 review describes this yeast infection of the hair follicles as itchy bumps of the same size on the upper chest, back and shoulders, with no blackheads. It says sweat and skin covered by clothing play a role in it returning, and that antibiotics taken for acne almost never help. See fungal acne.
• Folliculitis. The AAD says hair follicles are easier to damage "when your skin is damp and hot," such as when tight clothing rubs during a bike ride on a hot day. The spots look like a sudden acne breakout, each with a red ring. See body acne or folliculitis.

Clue	Points toward
Prickly, itchy spots after heat that fade in a few days	Heat rash
Itchy, same-size bumps on the upper trunk, no blackheads	Fungal acne
Sudden spots around hairs, each with a red ring	Folliculitis
Rough bumps under a strap or pad that turn into pimples	Acne mechanica
Blackheads, whiteheads and pimples of mixed sizes	Ordinary acne

Before, during and after a workout

The AAD says you can keep exercising and still see clearer skin. Its checklist:

Before

1. Put on clean workout clothes, washed since you last wore them. The AAD says "dead skin cells, bacteria, and oils on unwashed clothes can clog your pores."
2. Outdoors, apply an oil-free, broad-spectrum, water-resistant sunscreen with SPF 30 or higher. The AAD says the sun can dry the skin, which can lead the body to make more oil.

During 3. Pat sweat off with a clean towel. The AAD says rubbing your skin can make acne flare. 4. Avoid sharing helmets and shoulder pads when you can, and wipe off shared equipment before you use it.

After 5. Shower soon after you finish, using a mild, oil-free cleanser applied with your fingertips and warm water. The AAD says rubbing and hot water can make acne flare. 6. If you cannot shower, change out of your workout clothes and wipe skin that breaks out with a salicylic acid pad.

Towels matter too. The AAD says to use a towel "that has been washed since you (or someone else) last used it."

The AAD also suggests loose-fitting workout clothes made of cotton or sweat-wicking fabric, a type of fabric that pulls sweat away from the skin.

Does sweating clear your pores?

Some people hope a hard workout will "sweat out" acne. Skinli found no study showing that sweating clears pores or acne, and in the 2008 trial, exercise did not change acne on the trunk over 2 weeks. The AAD's advice is to keep exercising while you manage sweat and rubbing.

Treating acne that sweat makes worse

If you already have body acne, the habits above work alongside treatment. The AAD says a benzoyl peroxide foam wash used daily can help control back acne, and a salicylic acid product often works well on acne from gear and clothing. See acne body wash and body acne spray. Give any product 6 to 8 weeks.

When to see a doctor

See a doctor if:

• Heat rash has not improved after a few days, as the NHS advises.
• Bumps itch and look alike, which can point to fungal acne.
• You have deep, painful lumps, or spots that leak pus.
• Acne from gear is still there after 6 to 8 weeks of treatment. The AAD says a dermatologist can help then, sometimes with a prescription medicine.

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