Armpits Smell Like Onions? Here’s What Your Body’s Trying to Tell You

For most of us, sweat is a part of everyday life. It’s normal to smell after a hard workout or on a particularly hot day. Fun fact: the sweat itself isn’t what’s causing the stink. Your sudden increase of body odor is actually from sweat mixing with the bacteria on your skin.

But why do your armpits sometimes smell like onions? Now that’s a pretty extreme smell that anyone would feel concerned (and let’s be real, maybe embarrassed) about.

Here, a dermatologist shares four reasons why your body odor can smell like onions, and how to get rid of it, so you can go back to feeling fresh and clean.

4 causes of armpits that smell like onions

1. Your hormones could be fluctuating

Hormonal fluctuations can play a role in body odor, says Azadeh Shirazi, MD, FAAD, a board-certified dermatologist and founder of AziMD Skincare. Yep, you may smell different during your “time of the month.” Research even suggests your body odor slightly changes during ovulation in order to attract a mate, according to the Cleveland Clinic. (Mother nature works in mysterious ways!) This could also explain why you may smell like onions when you’re pregnant—your body is ramping up hormones to support pregnancy, especially in the first trimester.

Other times you might notice a change in body odor is during menopause or times of high stress, says Dr. Shirazi. “With a decline in estrogen during menopause, higher levels of testosterone dominate, thereby attracting more bacteria to your sweat and causing it to smell stronger. Higher cortisol levels associated with stress can also have a similar effect,” she adds.

Also, thyroid problems can have an indirect effect on body odor, per the Cleveland Clinic. An overactive thyroid, for example, releases high levels of thyroid hormones, causing changes in your usual body scent. If you suspect you’re having a thyroid issue, talk to your doctor. They can run some blood tests to help figure out your best course of treatment.

2. You have an underlying condition

If your BO smells like onions all of a sudden, it could be a sign of an underlying health condition that needs attention and treatment, especially if you’re sweating excessively. The medical term for excessive sweating is hyperhidrosis, per the Cleveland Clinic, and it can be a side effect of other conditions like diabetes, overactive thyroid, or liver issues, among others.

While hyperhidrosis can feel embarrassing, it’s a super common condition. Remember: your sweat itself is odorless, but the more sweat you produce, the more likely the bacteria on your skin will mix with it and make you smell a bit off.

According to Dr. Shirazi, there’s also a condition called bromhidrosis—where the bacteria on your skin breaks down the sweat and causes a sulfur or onion-y smell. “This odor is more powerful than ordinary sweat,” she adds.

3. It’s your diet

We’ve all heard the popular phrase, “you are what you eat.” And in this case, the food you’re eating might literally make you smell like onions. “Diets rich in spices or ingredients like garlic and onion can change and affect body odor,” adds Dr. Shirazi. Other foods that could cause body odor include the following, per the Cleveland Clinic:

• Red meat
• Cruciferous vegetables (cauliflower, broccoli, cabbage)
• Asparagus
• Fish
• Alcohol

There are also certain chemicals in food that can increase bacteria. This bacteria then produce a chemical called trimethylamine—the same one responsible for the stinky odor fish and other aquatic animals give off, per the American Chemical Society.

“Trimethylamine in the digestive system can also cause more pungent odor from your armpits,” says Dr. Shirazi. “This can especially be seen with liver or kidney diseases.”

“Diets rich in spices or ingredients like garlic can change and affect body odor.” —Azadeh Shirazi, MD, dermatologist

4. You’re getting older

Why is it that everything seems to change with age? From the color of our hair to the way our bodies move, aging brings about all sorts of new experiences—including the way we smell. If you find yourself smelling like onions in the morning, or during other times where you’re not necessarily sweating, it could simply be a product of getting older.

Body odor can change as we age due to increased levels of 2-nonenal, says Dr. Shirazi. It’s another chemical compound that causes a musty odor. This chemical naturally increases in our bodies as we get older, and is often deemed the stereotypical “old person smell,” even though it’s perfectly natural and can be mitigated with hygiene practices like showering daily and using odor-neutralizing products.

How to get rid of onion-smelling armpits

If you’ve ever been worried you’re going to clear a room with your stench, there are ways to help decrease those odds. Here are some top tips to get your armpits smelling fresh and clean.

Apply deodorant

The first line of defense (and likely the most obvious) is finding a good deodorant. But keep in mind, there’s an important difference between deodorant and antiperspirant.

“There’s a notable distinction between deodorants and antiperspirants, even though they serve the same purpose to reduce body odor,” says Dr. Shirazi. “Deodorants mask the smell of body odor usually with fragrances, while antiperspirants use aluminum salts that dissolve and block sweat from forming.”

So, if your armpits still smell like onions even after putting on deodorant, it might be worth trying an antiperspirant instead, especially if you tend to sweat a lot.

TIP

If your armpits smell like onions even right after showering, make sure you’re thoroughly washing your armpits with an antibacterial soap and lathering for at least 30 seconds.

Try home remedies or lifestyle changes

According to the Cleveland Clinic, there are a few home remedies you can try to help stop smelly body odor. A few include:

• Baking soda: Applying a paste of baking soda and water may help balance acid on your skin and reduce odor.
• Green tea bags: Placing green tea bags soaked in water on your armpits for a few minutes each day may help block pores and reduce odor.
• Apple cider vinegar or lemon juice: Spritzing a dash of apple cider vinegar or lemon juice mixed with water in a spray bottle can help kill bacteria on the skin (just make sure you don’t have open cuts or recently shaved; the acidity could slightly burn!).

There are also some lifestyle habits you can incorporate to help your pits stay dry, including the following, per the Cleveland Clinic:

• Keeping armpit hair shaved (or trimmed)
• Wearing loose-fitting or cotton clothing
• Removing smelly foods from your diet
• Reducing stress levels

Ask about dermatologist-recommended products

A dermatologist can also recommend tried-and-true products they know can give you results. “I have my patients use a product with glycolic acid, like the AziMD Skincare Clarify pads, three times a week as it reduces odor-causing bacteria and exfoliates the skin, minimizing the smell. It’s also gentle enough to use in the delicate armpit skin.”

Your dermatologist may also offer a prescription-strength antiperspirant to apply once or twice daily if you deal with hyperhidrosis.

Consider botox

If prescription-strength products are not working, there’s also Botox. Yep, you read that right. Botox isn’t only for reducing face wrinkles; it can also help you manage other medical conditions, including excessive sweating. After several injections in your armpits, your underarm sweat should lighten up, per the Cleveland Clinic.

Just keep in mind: not every insurance provider fully covers Botox treatment. If you’re unsure whether you’re covered, call your insurance company, or ask your doctor about alternative options.

When to see a doctor

Most of the time, smelly BO is nothing to be concerned about. It happens to the best of us, and can easily be neutralized with proper hygiene and odor-reducing products.

That said, if over-the-counter measures are not controlling your onion body odor and excessive sweating, then it’s best to see your doctor, says Dr. Shirazi. A comprehensive checkup can help determine whether your body odor and health are at all connected, and exactly where the smell is coming from.

—reviewed by Jennifer Gilbert, MD, MPH