We've all done the "turn and whiff" — you know, when you try to slyly turn your head to see if your pits are stinking up a storm? But what happens when that smell is…onion-y?
Actually, it's not all that weird, because some people just smell like onions.
"Sweat feeds the bacteria present on the skin, and that bacteria produces an odor," Deirdre Hooper, MD, a board-certified dermatologist at Audubon Dermatology in New Orleans, Louisiana, tells LIVESTRONG.com.
And everyone has a different microbiome (the diverse colony of microorganisms like bacteria that live all over your body), which is influenced by things like diet, stress, environment and genes.
"The reason why someone's sweat smells stinkier is based on their own microbiome. It doesn't mean that you're dirty," Dr. Hooper says.
A January 2015 study in Microbiome swabbed the underarms of 24 white men and women. They found that those who didn't use antiperspirants tended to have about 50 times more bacteria than those who swiped with these topical sweat-stoppers. Interestingly enough, armpit odors ranged from "sulfury-cat urine" to "acid-spicy," "foot" (moldy) and "fresh onion."
Bottom line: If your armpits smell like onions, you just happen to have that type of bacteria that gives you that odor.
How to Stop Armpits From Smelling Like Onions
So, here's the deal: There isn't good science to support that diet changes (like eliminating garlic or onions) is going to make a difference.
"You can try it, but my advice is keeping the sweat under arms to a minimum," Dr. Hooper says.
Because sweat feeds bacteria, stopping sweat will be the best way to control underarm odors, onion-y or not:
1. Clean Those Pits
"A good 10 to 15 seconds of massaging a cleanser into underarms will do a nice job of temporarily ridding bacteria in this area," Dr. Hooper says.
2. Dry Them Well
Here's a trick worth trying, Dr. Hooper says: After you shower, use a blow dryer to fully dry your underarms. Use a warm — not hot — setting and stop before/if any redness occurs.
The dryness creates a less-friendly environment for bacteria to flourish. If you notice any other folds of your skin smell — under the breasts, on your belly, in your groin — you can use the hairdryer to dry those areas, too, she says.
3. Use Antiperspirant
OTC and prescription-strength antiperspirants are available. These traditionally use aluminum to temporarily plug sweat ducts, though some natural antiperspirants use alternative ingredients to decrease sweating. (There is no scientific evidence to say that an antiperspirant will up your risk of cancer or other major health risks, though talk to your doctor if you have severe kidney disease, advises Penn Medicine.)
In the 2015 Microbiome study mentioned above, people who had a more intense onion armpit odor were those who didn't use antiperspirants.
4. Consider Botox
If antiperspirants are not enough and sweating is extremely bothersome for you, talk to your doctor about whether you're a good candidate for Botox injections.
"This is a safe and effective way to decrease sweating," Dr. Hooper says. It's also perfectly OK to stop sweat in this area — your body won't have problems cooling itself off because your armpits aren't sweating.
Insurance may cover Botox after you've tried other treatments, so ask about their requirements.