What's the Deal with Antimicrobial Underwear

Ask Dr. Jen

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Underwear that is marketed as antimicrobial or antibacterial is made of a fabric designed to reduce the growth of microorganisms, typically certain bacteria. Often, the fabrics are impregnated with zinc or silver, but there are apparently a variety of methods to achieve this goal. Is this a real advance or just another way to profit by making women worry that they smell and/or capitalize on the fact that many women with vulvar or vaginal conditions are often inappropriately diagnosed and/or treated?

As antibacterial underwear is also marketed to men, I can’t say it’s all the patriarchy, but it does seem that these products were first targeted to women, and the marketing for some of these products certainly seems to imply a health benefit and that doesn’t seem to be the case for men. For example, here is an Instagram screenshot from one brand, hûha. On their Instagram, there is an anecdote from a consumer about their underwear apparently reducing bacterial vaginosis. As an aside, anecdotes are a great way for any company to avoid making medically unsubstantiated claims themselves; they can let consumers do it, and you fill in the blanks. This irritates me regardless of the product.

The first question we should be asking is, does this product fill an actual health void? There is no evidence that regularly laundered underwear is a cause of any health concern. Wearing a fresh pair of underwear that you like and are comfortable with is just fine, but if you find yourself caught on a trip and there is no ability to wash your underwear, wearing a pair twice is really unlikely to cause harm. There is a case report of someone who wore the same pair of underwear unwashed for 10 years having very serious skin issues, but this is over 10 years and happened due to a combination of complex reasons. As an aside, new underwear is something to think of if you fill Amazon wishlists for shelters or for people who deliver packets to the unhoused. I always buy underwear and socks to donate when they are on the list. 

Underwear that fits poorly so that it chafes or digs into the skin can damage the acid mantle and could lead to bacterial and yeast overgrowth, skin breakdown, itching, and/or irritation. This is a condition called intertrigo, and it is seen in places where the skin rubs together, often in the groin. Intertrigo is red, rash and can be itchy and/or painful. Fabric that increases sweat or traps moisture can also contribute to intertrigo, as wet skin has a higher friction coefficient than dry skin, and so the rubbing can cause more damage to the skin, and the moisture likely also contributes to the growth of bacteria and yeast. 

This means that underwear that is so tight or poorly fitted that it digs into the skin or underwear that stays wet, keeping moisture against the skin, could cause issues. This will often pose a comfort issue well before it creates a health issue. While antibacterial underwear hasn’t been studied here, the best first step for any of these issues is underwear that fits well, doesn’t chaff, and wicks moisture away from the skin. Different people may prefer different fabrics and fits, and that’s okay. Synthetic garments get a bad rap here, likely due to the lack of a “natural health halo,” but some modern synthetics are excellent at wicking water from the skin.

What about underwear causing vaginal infections, meaning inside the vagina, not on the vulva or skin surface? As underwear is outerwear, it can’t change what is happening inside the vagina; the only way that underwear could contribute to vaginal infections would be by changing yeast colonization on the skin. If there is a greater yeast reservoir on the skin surface, that could potentially be a source of infection. There is one study that showed a link between tight-fitting clothing, including underwear, and yeast infections, but it’s a cross-sectional study, meaning they tested for yeast and then asked women about the clothing they wore in the past four weeks. There are a lot of reasons this study shouldn’t be used to conclude cause and effect. There are at least three studies that show no link between underwear and yeast infections. One is a retrospective study of university students in the United States, but obviously, that comes with all the issues of a retrospective study. A study from Spain followed female sex workers for four years and found no association between tight-fitting clothing or synthetic underwear and yeast infections, and a study from Ukraine also found no increase in yeast colonization on the skin with either tight-fitting clothing or synthetic underwear. 

No study has looked at underwear and bacterial vaginosis or urinary tract infections, but biologically, I think it is highly implausible that there could be a connection.

What about thongs? One study looked at thongs and bikini-style underwear, both with pantyliners (thong-style and regular), and there was no difference in vulvar microclimate, skin pH, or bacteria on the skin. While this study isn’t underwear by itself, but rather underwear with a pantyliner, the lack of difference between the two is still encouraging. 

Okay, but what about the antimicrobial underwear?

There are no studies that I could find evaluating anti bacterial underwear for health benefits. Might they cause less stink in a gym bag? I have no idea, and truthfully, that’s outside of the medical realm, but sure, they might. I could make a case for trying antimicrobial underwear (as they typically claim to be odor-resistant) for someone with a persistent genital odor no cause can be found after a thorough evaluation. Another situation might be someone who is suffering chronically from intertrigo. I fully admit these situations are a stretch, medically speaking. For chronic intertrigo, this should in no way replace the standard therapies of cleansing daily, treating an active yeast infection, keeping the skin dry, avoiding chaffing, using topical anti-fungal powders preventatively, and treating diabetes if present. 

There is a lot of underwear lore. 

Almost every woman has been told at least once (and often more than once) to wear white cotton underwear as a medical recommendation. Either to prevent yeast infections or other infections or to prevent some other kind of vaginal mayhem, although I have yet to hear an actual biologically plausible explanation of how black or red underwear or a lace thong could be the harbinger of a vaginal or vulvar apocalypse. If black, red, or navy fabric were “bad” for the skin, why is this health warning limited to underwear? Why not pants or towels?

The answer here is almost certainly equal parts ignorance and purity culture. Old myths from before we knew much about vaginal infections die hard. And, of course, patriarchal myths are the most resilient. I would bet that decades ago, the idea of white cotton underwear came from an awful “good girls don’t get infections” trope because, of course, “bad girls” wore black or red or lace underwear. Insert massive eye roll.

As stated earlier, underwear just needs to not be so ill-fitting that it chafes, and the fabric shouldn’t keep moisture against the skin. In most cases, if your underwear happens to be this tight, it is likely to be uncomfortable long before you get skin injury, but sometimes you get dressed in a hurry, and then all of a sudden, you are tugging at your groin wondering why things are so uncomfortable, and you realize that you are wearing a pair of your kid’s underwear (true story, happened to a gynecologist friend, and no, not me) or you are wearing those old, ill-fitting panties that you mean to throw away but instead forgot and washed them and here you are (this has happened to me). 

Like many things that belong in the Journal of Old Wives Tales, the underwear-vaginal mayhem connection is based on a little bit of knowledge and a heaping dose of patriarchy. As long as your underwear fits correctly, does not trap sweat against your skin, and doesn’t cause friction, it’s almost certainly fine. If you want to buy antimicrobial underwear because you think it makes your gym bag less stinky, you be you. If you like the antimicrobial brands for other reasons, you be you. If you find a specific fabric and the feel is perfect, go for it. But until there are actual studies with these products, don’t feel you need to spend money on them or be worried that you are somehow missing out, medically speaking, because based on the current evidence and the basic biology, antimicrobial underwear sounds more like a solution looking for a problem. 

References

Adachi MM, Yoshida K, Fukuchi T, Tanaka A, Yamamoto N, Sugawara H. Extensive chronic perianal pyoderma associated with persistent inflammation caused by wearing the same unwashed underwear for more than ten years. Clin Case Rep. 2023;11:e7477.  

Runeman B, Rybo G, Forsgren-Brusk U, et al. The Vulvar Skin Microenvironment: Impact of Tight-fitting Underwear on Microclimate, pH and Microflora. Acta Derm Venereol 2005; 85: 118–122.

Elegbe IA, Elegbe I. Quantitative relationships of Candida albicans infections and dressing patterns in Nigerian women. Am J Public Health 1983;73:450-2.

Otero L, Palacio V, Carrero F, Mendez FJ, Vazquez F. Vulvovaginal candidiasis in female sex workers. Int J STD AIDS 1998;9:526-30.

Geiger AM, Foxman B. Risk factors for vulvovaginal candidiasis: a case± control study among university students. Epidemiology 1996;7:182-7.

Mårdh P-A, Novikova N, Stukalova E. Colonisation of extragenital sites by Candida in women with recurrent vulvovaginal candiosis. BJOG: an International Journal of Obstetrics and Gynaecology. 2003;110:934–937.