There’s a lot of chatter on the Internet about what to wear and what not to wear when it comes to underwear and how it can affect genital health, for both women and men. Whether you call them drawers, skivvies, butt huggers, briefs, panties, knickers, tighty-whities, or just simply undies, here are six questions you may have about them. Our answers are based on a search of the scientific literature, though, perhaps not surprisingly, there’s not much well-designed research on underwear out there. A lot boils down to common sense and what works for you.
Does the type of fabric matter?
It can make the difference between your genital area feeling hot and sweaty or cool and dry. Plus, it may play at least a small role in certain vaginal infections, some research suggests.
According to an older epidemiological survey in the European Journal of Obstetrics & Gynecology and Reproductive Biology, one of the factors associated with vaginal yeast infections is wearing underwear made from synthetic fabrics (such as nylon and lycra), which don’t “breathe” and thus keep the genital area warm and moist, perfect conditions for the growth of yeast. Though not all the literature supports this connection, many clinicians advise that women prone to yeast infections wear “breathable” panties, such as those made from “wickable” fabrics, which can be purchased online or in some sporting-goods stores.
Along similar lines, women with recurrent infections are often advised to not wear tight pants, body-shaper undergarments, or pantyhose. Keep in mind, however, that other factors play a more significant role in the development of vaginal yeast infections than your underwear, including whether you take antibiotics or oral contraceptives, are pregnant, or have poorly controlled diabetes.
What about thongs? Bad idea?
Some women report that they notice an increase in urinary tract or yeast infections when wearing thongs; and some physicians recommend against them for women prone to vulvar irritation and vaginitis. Thongs are tight against genital and anal areas, so they may inflame sensitive skin there.
And the undies may slide back and forth, especially when you exercise, which could, at least in theory, transfer fecal bacteria from the anus to the urethra, possibly resulting in a urinary tract or vaginal infection. However, in a study in Acta Dermato-Venereologica, “string panties” were not significantly associated with an increase in anal bacteria in the vulvar area.
Boxers or briefs? Is there really a relationship between men’s underwear and fertility?
It’s commonly said—but without definitive evidence—that wearing tight briefs as opposed to loose boxers may adversely affect sperm, because this subjects the testicular area (where sperm are formed and stored) to elevated temperature. A small study in Fertility and Sterility found that men who wore specially designed underwear that increased heat in the scrotal area for 15 hours a day over 120 days had temporary decreases in sperm count, motility, and viability.
In another paper, in Reproductive Biology, wearing boxer shorts was associated with a lower risk of having poor sperm quality. But an earlier paper, in the Journal of Urology, found no significant temperature difference in the scrotal area among men who wore boxers or briefs. If you are a man having trouble conceiving, it can’t hurt to switch to boxers (and, for similar reasons, to avoid hot baths, hot tubs, and saunas).
How often should you change your underwear?
Many people routinely put on a clean pair every day, but there’s no consensus that this impacts health in any major way—and practices vary culturally. In a study from Iran, published in a World Health Organization journal, more frequent changing of underwear was associated with a reduced rate of urinary tract infections in pregnant women.
But a subsequent Turkish paper in Gynecology & Obstetrics noted that vaginal infections were not significantly related to how often university students changed their underwear. For cleanliness and comfort at the very least, we’re in favor of a daily donning of fresh underwear (or more often if you work up a sweat or your undies otherwise get wet or soiled).
What’s the deal with antibacterial underwear?
Made from textiles with antimicrobial properties, this special underwear is marketed to prevent odors. Though it’s not always clear from the labels, the antimicrobial effect often comes from silver or nanosilver (ultra-small particles of silver).
But there’s concern that exposure to silver, especially nanosilver, may disrupt the body’s natural bacterial balance and have other adverse effects. There are also unresolved questions about the potential negative impact that silver-treated textiles have on the environment when the garments are laundered.
Another antimicrobial used in underwear fabric is triclosan, a chemical that has been linked to hormonal changes in animals and may be contributing to antibiotic resistance.
In any case, any deodorant effect these panties might have would likely be small and temporary. And they are completely unnecessary. Just change your underwear regularly—and always after a hot, sweaty workout.
Do you need to wear underwear at all?
While most of us don’t think about going out undie-less, some people like the airy feel, especially on hot and humid days. It’s also more comfortable to forgo underwear if you cycle or otherwise work out in seamless-crotch cycling shorts that are breathable and wickable (underwear under them can bunch up and irritate skin).
Also, many people like to sleep without underwear. Some papers give a general recommendation for women with vaginal infections to go bare at night, though an older (1992) review paper in Obstetrical & Gynecological Survey noted that this did not make a difference in terms of symptoms. The bottom line: If going commando is comfortable, go for it.