Can Your Sweat Really Bleach Your Clothes?

Ever notice white stains on your gym shirt after a workout, or on a hot, humid day? Is it a coincidence, or is your sweat really bleaching your clothes?

We spoke to a dermatologist to set the record straight on what causes those pesky, bleach-like stains and how to deal with them.

First, some quick background: We have two types of sweat glands, eccrine and apocrine. "Eccrine sweat glands are all over the body, while apocrine sweat glands tend to be focused on the scalp, underarms and groin," dermatologist Erum Ilyas, MD, CEO and founder of AmberNoon, tells LIVESTRONG.com.

Apocrine sweat glands may be the main culprit behind bleachy stains. Why? They're bigger, more concentrated and mingle with bacteria to produce body odor and other reactions more often than eccrine glands, according to an October 2020 StatPearls review.

That lingering sweat can then contribute to stains in a number of ways:

Sweat has an acidic pH due to micronutrients like ammonia and bicarbonate (one of the ingredients in baking soda), according to a 2019 review in ‌Temperature‌.

And that acidity could contribute to white sweat stains, Dr. Ilyas says. "It is likely the acidic pH of sweat interacting with textile dyes and antiperspirants that leads to this [bleaching] effect."

However, the topic isn't well-studied, so more research is needed to establish this link.

Another cause of white sweat stains? The very product you use to curb them.

Sweat is naturally colorless, according to the U.S. National Library of Medicine. But the minerals in sweat can react with your deodorant to form stains, Dr. Ilyas says. Deodorant can also leave a white film on your skin that sticks to your clothing and discolors the fabric over time, she adds. This is often due to benzoyl peroxide, an antibacterial that is added to deodorant to decrease armpit odor but is a known fabric bleaching agent.

"Sweat can combine with aluminum in antiperspirants to leave a yellow residue on clothing, and the residue from an antiperspirant can also contribute to these stains," she says.

Sweat can combine with the dye in your clothes to create those dreaded stains, according to Dr. Ilyas.

"The pigments in textiles can interact with sweat to alter the color and potentially lighten or create a bleaching effect on clothing," she says.

Ever notice salt on your clothing after exercise? As your sweat evaporates after a gym session, it can leave behind salt to crystalize and form white stains, according to Columbia University.

While anyone can develop sweat stains, there are some people who may be more susceptible to bleachy marks.

Athletes and people who are otherwise physically fit may have more opportunity to sweat, and, as a result, more chances for those white stains to develop, Dr. Ilyas says.

Athletes may also simply produce more sweat than non-athletes. A small April 2014 study in ‌PLOS One‌ observed 16 long-distance runners and 20 sedentary people, and found that the runners sweat faster and more profusely when their sweat glads were activated compared to the non-runners.

However, this is one of the only recent studies to measure this discrepancy, so more research is needed to support the findings.

Higher concentrations of salt in your sweat can also leave your clothing vulnerable to stains, Dr. Ilyas says.

People who exercise for long periods of time (defined as more than an hour and a half of activity) in the heat, like marathoners, can excrete higher amounts of salt in their sweat, according to a July 2016 study in the ‌Journal of the International Society of Sports Nutrition‌.

Some health conditions can also make your sweat saltier. For example, cystic fibrosis affects how water and salt move through your body and can result in high levels of chloride (a component of salt) in sweat, according to the Cleveland Clinic.

Excessive sweating can be a symptom of health conditions like hyperthyroidism, menopause or medication side effects, according to the Mayo Clinic. You may also have hyperhidrosis, a skin disorder where your sweat glands go into overdrive and make you sweat a lot, per the Cleveland Clinic.

Whatever the cause, that extra sweat can up the chances of stains on your clothing, Dr. Ilyas says.

While some discoloration may not be completely avoidable over time, there are ways to minimize bleaching and sweat stains.

Don't head off to your workout class without putting on antiperspirant, Dr. Ilyas says. Not only will your fellow gym mates be happier, but you may be able to decrease the chances of stains and bad odors.

No need to go overboard, though, Dr. Ilyas says: "Apply a thin layer of antiperspirant to reduce the chances of the product causing its own discoloration."

Another tip for how to prevent sweat stains in the first place? Put on antiperspirant the night before to give it ample opportunity to soak in as you sleep. "Antiperspirants are effective for longer than a few hours, so it is OK to apply the night before," she explains.

If yellow stains are also a problem for you, consider using an antiperspirant with a lower concentration of aluminum or an aluminum-free natural deodorant, Dr. Ilyas says. She also recommends using a prescription gel antiperspirant, which leaves behind minimal residue and thus reduces the odds of stains.

Prevent and remove sweat stains by washing your sweaty clothes ASAP, Dr. Ilyas recommends: The longer they sit there, the more the discoloration can set in.

If you're prone to excess perspiration and can't seem to keep it under control, chat with your doctor about medicated antiperspirants.

If that's not enough, Dr. Ilyas suggests talking to your doctor about Botox injections. They can temporarily relieve excessive sweating, according to April 2013 research in ‌Toxins.‌Your doctor may also suggest pills or wipes for treatment.

It's worth noting that Botox treatments are effective only at the site of injection. For example, injections into the armpits will temporarily reduce sweating in the armpits but will not limit sweating elsewhere. The effect of Botox injections typically lasts three to four months.