"More Women Choosing Not to Wear Underwear at the Gym"... Is the Claim That 'No Underwear Spreads STIs' True?

The STI Transmission Rumor Is Baseless

The Real Concern: Skin Diseases Caused by Sweat, Moisture, and Friction

A hygiene debate has emerged overseas regarding the so-called “no underwear workout,” where people forgo wearing underwear inside leggings or workout clothes at the gym. The controversy has intensified due to concerns about sweat or bodily secretions getting on shared gym equipment and even claims that sexually transmitted infections (STIs) could be spread this way. However, experts point out that it’s important to distinguish between transmission routes for STIs and skin diseases. They explain that more important than simply whether or not you wear underwear is following basic hygiene measures, such as removing wet workout wear promptly after exercising and washing it properly.

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According to the UK outlet Metro, a recent survey conducted by lingerie brand Pour Moi of 1,500 women revealed that 5% of respondents said they either never or very rarely wear underwear when working out at the gym.

As the survey results spread online, reactions were divided. Some said that it's uncomfortable for underwear to get sweaty during exercise or that they want to avoid visible underwear lines under leggings, so they opt to go without. Others argued that, since many people share gym equipment, consideration for hygiene is necessary.

The controversy was further fueled by rumors of STI transmission that rapidly spread on social networking services (SNS). In 2024, stories circulated on TikTok and other platforms claiming, "Even though I did not have sexual intercourse, I contracted chlamydial conjunctivitis, a sexually transmitted infection, after wiping my face with a shared gym towel." Subsequently, the rumor escalated to claims that "sweat or bodily secretions from users not wearing underwear can get on gym equipment seats, which could transmit chlamydia or other STIs to others." These claims heightened fears among gym users.

"Chlamydia Infection from Shared Equipment?"... Experts: "Baseless Rumor"

However, experts dismiss the notion of chlamydia being transmitted through gym equipment, towels, or toilet seats as "a groundless myth with no medical basis." Dr. Jo Whittington, an emergency medicine physician in the United States, stated, "Chlamydia trachomatis, the bacteria that causes chlamydia, is only transmitted through direct sexual contact involving bodily fluids." She further explained, "This bacterium cannot survive long on dry surfaces or equipment outside the human body, so the risk of infection through contact with gym equipment or shared items is virtually zero."

The UK’s National Health Service (NHS) also clarified in its official guidelines that chlamydia is spread only through direct sexual contact or exposure to an infected person’s bodily fluids, and is not transmitted through towels, bathtubs, swimming pools, toilet seats, or other everyday contact with objects.

Skin Diseases from Friction Are a Bigger Risk than STIs

However, experts warn about the risk of “skin diseases” that can arise if you go without underwear. Wearing only tight workout clothes during intense exercise, without underwear, can actually increase the risk of issues like dermatitis or fungal infections—not STIs.

British general practitioner Dr. Ashiya Maula explained, "Cotton underwear acts as a protective barrier by absorbing sweat and moisture produced during exercise and reducing direct friction between the skin and workout clothing." Dr. Maula pointed out that, if you wear tight leggings without underwear and do exercises with a lot of lower body movement—such as running or cycling—the inner thighs and groin area can be repeatedly chafed, leading to soreness, redness, and skin irritation.

Additionally, if sweat and bodily secretions are absorbed directly into workout clothes and stay in prolonged contact with the skin, a warm and moist environment forms, making it easier for bacteria and fungi to multiply. This increases the likelihood of issues such as tinea cruris (groin ringworm), folliculitis, or candidal vaginitis. According to information from Asan Medical Center, habits like wearing excessively tight pants for extended periods or leaving them damp are major exacerbating factors for candidal vaginitis, which causes vulvar itching, pain, and abnormal discharge.

The Key Is Not Underwear, But Moisture Management and Cleanliness

So, does this mean you must always wear underwear for good hygiene? According to British GP Dr. Rupa Parmar and the Center for Young Women's Health at Boston Children’s Hospital, as long as your workout clothing is sufficiently thick and breathable, going without underwear is not inherently dangerous to your health. In fact, wearing sweat-soaked underwear for a long time can create a hot and moist environment, promoting conditions like tinea cruris or bacterial overgrowth. Dr. Parmar emphasized, "What matters more than a single extra layer is how quickly you remove sweat and moisture and maintain cleanliness."

This content was produced with the assistance of AI translation services.