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?
If you're wondering why your body odor smells like onions, just know that it's not all that weird. Some people just smell like onions.
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Here's why that can happen, plus tips for how to get rid of onion-smelling sweat.
What Causes Body Odor to 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.
When sweat mixes with bacteria, it creates a sulfur-containing organic compound called thioalcohols. So, the higher amount of bacteria you have, the more you may smell.
Here are some reasons why bacteria causes odor.
It's Your Microbiome
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.
You may even have only one armpit that smells bad, because it is naturally sweatier than the other.
You're Not Using Antiperspirants
A January 2015 study in Microbiome swabbed the underarms of 24 white people. 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."
Antiperspirants are different from deodorants, which simply mask the odor in your pits. Antiperspirants reduce the amount that you sweat.
You Have Bromhidrosis
Bromhidrosis is the medical term for excessive, foul-smelling sweat, per an October 2019 study in JAAD Case Reports. This can happen with a condition called hyperhidrosis, or excessive sweating in the palms, feet, armpits etc., per the Mayo Clinic.
A combination of these conditions can make your sweat smell like onions.
You Have a Chronic Illness
If you start to notice your BO getting extra smelly all of a sudden, it may signal an underlying health condition. Liver disease, kidney disease and hyperthyroidism can lead to excessive, onion-smelling sweat, according to AARP.
Talk to your doctor if you are experiencing smelly sweat in addition to other concerning side effects.
What Does It Mean If Your Sweat Smells Sweet?
Sometimes, your sweat can smell sweet. This can indicate an underlying health condition.If it's fruity, you could be dealing with diabetic ketoacidosis — when people with diabetes' blood glucose levels are too high. If your sweat smells like maple syrup, you could be dealing with maple syrup urine disease — a rare genetic disorder. Talk to your doctor if you experience either of these.
You Are Going Through Hormonal Change
When preteens begin puberty, their hormones fluctuate, which can cause their body odor to smell.
Hormonal imbalances (such as an increase in estrogen) can also cause body odor. Talk to your doctor if you have other hormone-related side effects.
How to Stop Armpits From Smelling Like Onions
So, here's the deal: There isn't good science to support that eating onions gives you BO. And, diet changes are not going to get rid of onion-smelling sweat.
"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.
If your armpits still smell after showering, try implementing some of the following steps.
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, which can help prevent sweat from smelling like onions. If you notice any other folds of your skin smell — under the breasts, in your bellybutton or 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, per 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.
- Penn Medicine: “Is Deodorant Harmful for Your Health?”
- Microbiome: “Mapping axillary microbiota responsible for body odours using a culture-independent approach”
- JAAD Case Reports: "A case of axillary bromhidrosis secondary to trimethylaminuria successfully treated with microwave-based therapy"
- Mayo Clinic: "Hyperhidrosis"
- AARP: "What's That Smell? Possibly a Health Issue"
- Cleveland Clinic: "Body Odor:
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.