You take a quick whiff of one underarm and notice that it seriously reeks. But when you go to check the other? Nada. No weird smells there! So...what's going on?
Body odor under one armpit only may seem a little bizarre, but it also might be more common than you think. "I get asked about this a lot in the office setting," says Marisa Garshick, MD, assistant clinical professor of dermatology at Cornell-New York Presbyterian Medical Center. Ah, so you and your funky pit aren't alone after all!
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Better still, the underlying cause is often surprisingly straightforward and easy to fix. Here are five of the most likely reasons why one armpit may smell worse than the other, plus when to touch base with your doctor.
1. You Forgot to Put on Antiperspirant or Deodorant
Sure, it's the most obvious culprit. But it's also the most likely, Dr. Garshick says. While antiperspirants and deodorants work a little differently — the former blocks the production of sweat (which becomes stinky when it mixes with bacteria on your skin) while the latter simply masks sweat's odor — forgetting to apply either under one of your arms could easily cause a difference in smell.
Fix it: Pay attention when you're swiping and be sure to get both pits.
2. One Armpit Is Hairier Than the Other
Forgot to shave on one side or just didn't do as thorough of a job? Your fuzzier armpit may very well be a little smellier.
Because armpit hair traps more sweat than skin alone, there's more of an opportunity for sweat on the hairier side to mix with odor-causing bacteria, says Beth Goldstein, MD, adjunct clinical professor of dermatology at the University of North Carolina at Chapel Hill and founder of the skin care brand GETMR.
Fix it: Fortunately, the fix is pretty simple: Do a quick check to confirm that both underarms are equally shaven before getting out of the shower. Removing armpit hair via shaving or waxing is an effective way to reduce underarm odor, per a March 2016 study in the Journal of Cosmetic Dermatology.
3. One of Your Arms Has Been Working Harder Than the Other
Bodies don't behave 100 percent symmetrically.
"They don't always follow the textbook. Theoretically, someone could sweat more on one side than the other," Dr. Garshick says.
So if you're using the arm on that side more intensely — say, by carrying a heavy bag or purse on that shoulder for a long period — it's possible for that underarm to end up a little stinkier.
Fix it: Try to even out your arm use throughout the day by, for example, switching sides when carrying your bag or purse.
4. You Have Some Extra Stinky Bacteria Under One Armpit
Just like in the gut, the surface of our armpit skin has a mix of good and bad bacteria that normally coexist in relative harmony. But sometimes the balance can become disrupted, leading to an overgrowth of certain bad bacteria that could potentially make body odor more potent, Dr. Garshick says.
And if the bad bacteria are more prevalent in one underarm than the other, that pit might start to get noticeably noxious.
Fix it: Using a dedicated antibacterial body wash can help bring the bacteria — and its accompanying smell — back in check. Dr. Goldstein likes Dial Complete White Antibacterial Bar Soap ($5.31 for 8 bars, Amazon.com) or Hibiclens Antiseptic & Antimicrobial Skin Cleanser ($25 for 2 bottles, Amazon.com). "Use it daily or twice daily, without scrubbing," she says.
5. You Have an Infected Wound
Our underarms are packed with hair follicles, which can become more exposed after shaving. These follicles have the potential to get infected with bad bacteria living under the arm, causing the follicle to become red, inflamed, tender and even pus-filled, Dr. Garshick says. And sometimes, that inflammation and pus can have an unpleasant odor.
Fix it: Stopping shaving may be enough to help mild infections heal, notes the Mayo Clinic. But if it doesn't seem to be getting better on its own, you may need to see your doctor for a steroid or antibiotic cream.
When to See a Doctor
Occasionally having one particularly stinky pit isn't a big deal if you can easily pinpoint the culprit and get the stench situation solved — like remembering to put on antiperspirant or deodorant, shaving both sides equally, using antibacterial soap or even letting an infected hair follicle heal.
But you should call your doctor if the smell sticks around or gets worse even after trying at-home measures, or if you notice an unusual odor elsewhere on your body, Dr. Goldstein says. These could be signs of a possible illness like diabetes, liver disease or a problem with metabolizing certain foods or medicines.
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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.