This Is Why Gym Clothes Smell SO Bad — Even After You Wash Them

This Is Why Gym Clothes Smell SO Bad — Even After You Wash Them

This week, Mary decodes: Workout fabric.

Are you extra smelly after a workout? It might not actually be you. Your GYM CLOTHES could be the culprit.  

Over the past year, I’ve been trying to maintain a weekly intense workout session and hot yoga class and that’s when I started to notice that my clothes would reek ALL THE TIME! I’m not sure how many times I’ve had to rewash my leggings and t-shirts. They seem to smell like ammonia no matter how many times they go through the wash. After some research and investigation, I know why:



In a research study conducted at Ghent University, the overall odor of different clothing from a focus group was compared after an intense one-hour spinning class. They wore t-shirts made of either cotton, polyester, or a cotton-synthetic blend. The T-shirts were collected, sealed in plastic bags, and stored at room temperature in the dark, so bacterial growth occurred.

Results from an odor panel determined that the polyester clothing smelled SIGNIFICANTLY LESS PLEASANT. It was described as more intense, musty, strong and sour.  I can’t even imagine having to be on that odor panel smelling these sweaty, musty clothes!

So the study then analysed the bacterial composition of each fabric and what they discovered was the following.

All of the shirts grew several types of bacteria, but it was found that Micrococcus (a type of odor-causing bacteria) grew on:

  • 100% of the synthetic t-shirts worn in the study
  • 82% of the cotton-synthetic blend t-shirts worn in the study
  • 0% on the cotton t-shirts worn in the study.

It was even found that that stinky Micrococci bacteria grows better on synthetic fabrics than on your underarms! This explains why gym clothes seem to smell even worse than when our bodies sweat.


gym workout clothes - kaia naturals

Photo by Jelmer Assink.



“Moisture-wicking” or “Sweat Technology” often comes to mind when we think of workout clothes. I know I definitely look for that, because who wants to feel like a sweaty mess when working out. It’s hard enough to get yourself to the gym!

However, what you may not know is “moisture-wicking” basically means the clothing is made out of synthetic fabric like polyester, designed to keep you dry while you workout.

Polyester is a petroleum-based synthetic fiber and doesn’t have any natural properties which means it has very poor ADSORBING capacity. While your sweating, the moisture would evaporate THROUGH the fibres of your clothing instead of adsorbing INTO the fibres.


Adsorbing vs Absorbing

Adsorption = the process in which liquids from a substance adhere to a surface of the adsorbent.

Absorption = the process in which a fluid is dissolved by a liquid or a solid.


smelly gym clothes - kaia naturals

Photo by Linus Schutz.



Even though “moisture-wicking” means that fitness clothes will dry faster, the problem is bacteria from your sweat gets trapped IN BETWEEN the fibres as it passes through the garment.  

The bacteria that becomes trapped in between the fibres will create a pungent odor, we often smell in our gym bags and clothes. I think I just lost my appetite thinking about it!


Bacteria + Sweat = Odor


The more you wear the garment and sweat in it, the more bacteria and odor that will become trapped, making it even more difficult to wash out.


cotton fabrics

Photo by Jelmer Assink.



Cotton is a natural fiber (originating from the Gossypium cotton plant) almost entirely made up of cellulose, which gives it the ability to adsorb sweat and odor RIGHT INTO the fibres. This avoids bacteria becoming trapped in between the fibres and allows for better removal from the fibres when washed.

The weird part is, depending on whether you wear synthetic fabric or cotton, your workout clothes will end up smelling differently by the time they make it to the laundry hamper.



Photo by MNZ Store.



If stinky gym clothes are making your whole closet smell, don’t leave them sitting for a week before they make it into the wash. Bacteria LOVES a dark, cozy place like a gym bag or laundry hamper to grow even more bacteria.


  • Try hanging your clothes up to dry instead of throwing them damp directly in the hamper.
  • Wash your clothes immediately after you workout if you can.
  • Swap out your synthetic garments for cotton alternatives.
  • Use a sport laundry detergent designed for this type of bacteria.

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Boys Smell More… Is it true?

Boys Smell More… Is it true?

Do men tend to smell worse? This is a topic that often comes up from my women-run team at the kaia HQ. A few of them have asked me how to help their dads or boyfriends, and I quote them, “Not smell so bad.”

Why is it that many of us women deem men as the “stinkier” gender? Turns out, there are a few factors that put men on the smellier side and its not necessarily related to grooming.


Photo by Andi Wiskey.


Genetically speaking, a lot of men have more body hair than women. As hair is porous, it can easily trap odors and odor-causing bacteria. Have you ever sat by a campfire and found your hair smells like it shortly after? I still remember as a kid coming home from a campfire and waking up the next day with my hair still smelling like it.

Body hair can also trap moisture, especially with armpit hair. As it is in an enclosed area, it can trap more moisture and prevent sweat from evaporating, creating the perfect environment for odor-causing bacteria to thrive (sweat + bacteria = odor)

Therefore, a lot of men tend to say they feel drier and not as smelly when they’ve shaved.


Photo by Ivandrei Pretorius.


Unfortunately, men were genetically made up to have smellier armpits than women. Men typically have more ‘corynebacteria’ – the smelly bacteria, in their armpits than women do. Why? Men have thicker skin in their armpits and sweat more fatty  substances, which is the perfect recipe for corynebacteria to breed. So actually yes, boys do smell.


I hate having to describe the smell of a man after one of my favourite foods in the entire world….. CHEESE.   It has been found through studies that male sweat tends to smells “cheesy” because they have more of the molecule called, 3-hydroxy-3-methylhexanoic acid. On the other hand, Female sweat tends to smell oniony because they have more of the molecule 3-methyl-3-sulfanylhexan-1-ol. Both males and females have these two types of molecules that make our bodies sweat,  however they’re not present in equal amounts.

After mentioning this tidbit to the team last week, one of the girls today mentioned she actually could smell the “cheesy” sweat smell after she was stuck in a crowded subway between some sweaty guys.

Do you find the men in your life sweat a “CHEESY” smell? Let me know!


Photo by Andrew Neel.


If the men in your life are experiencing body odor, here are some tips that may help.

1. Shave

As body hair can trap odors, moisture and bacteria, removing the hair can help reduce odor and help them feel drier.

2. Avoid wearing synthetic fabrics

It was even found that odor-causing Micrococci bacteria grows better on synthetic fabrics like polyester and nylon. Choose natural, breathable fabrics like cotton.

3. Cleanse skin with antibacterial soap

It’s important to prime odorous areas of your body like the underarms by removing odor-causing bacteria. Look for ingredients like apple cider vinegar and sodium like the kaia naturalsthe underarm bar which eliminates bacteria on the skin and creates an inhospitable environment for odor-causing bacteria to grow.


4. Choose a cleaner diet

Eating processed, sugary foods can also cause body odor because these types of food lack chlorophyll, the compound that gives green vegetables their color. Chlorophyll is known for cleaning and deodorizing the blood, so foods that lack this compound will be more likely to cause the body to smell.

Why Sunscreen is The Best… Yet Caution is Required

Why Sunscreen is The Best… Yet Caution is Required

If someone asks what my desert island product is? It would definitely be SUNSCREEN. Ask any dermatologist and they’d tell you to ALWAYS wear sunscreen 365 days a year if you want healthy, young looking skin. More importantly, wearing sunscreen will help protect us from skin cancer. Skin cancer is the most common cancer in the U.S. and approximately 9,500 people in the U.S. are diagnosed with skin cancer every day.

Up to 80 percent of the sun’s UV rays can pass through clouds, which is why you should wear sunscreen even when it’s cloudy and raining outside. Sunscreen is a must-have for both beauty and health…but is it actually healthy for us? Like some deodorants, some sunscreens are actually toxic. Today, I’m decoding the difference between natural (mineral-based sunscreens) and chemical-based sunscreens.


why you need sunscreen - kaia naturals

Photo by lack of color.



There are two types of sunscreens: chemical and mineral. If you’re short on time and can’t be bothered with reading the details, just remember chemical = problem and mineral = better choice.  Here’s why: Chemical sunscreens work by absorbing the UV rays from the sun, converting them into heat, and then releasing the heat from our bodies. They usually contain a combination of these chemicals: oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate.

Although there are many other suspicious ingredients found in sunscreens, the one I’d like to focus on is OXYBENZONE.



Our skin absorbs oxybenzone like a SPONGE. A study from the EWG illustrated how sensitive our skin is to oxybenzone. Participants in the study who used chemical sunscreen had higher levels of oxybenzone in their bodies than those who did not. An even more interesting study showed correlations between eliminating usage of products containing oxybenzone and significantly lower oxybenzone levels in the body.



Oxybenzone is classified as an ENDOCRINE (hormone) DISRUPTOR. Endocrine disruptors alter the hormone levels in your body and are thought to lead to adverse developmental, reproductive, neurological, and immune effects. Hormones are the chemical messengers that travel in your body and are responsible  for coordinating complex processes like growth, metabolism, and fertility. They can influence the function of the immune system, and even alter behavior. More importantly, endocrine disruptors  have been linked to lowered fertility and an increased incidence of endometriosis and some cancers.  For reference, parabens, phthalates and synthetic fragrances are also all known endocrine disruptors.


sunscreen - kaia naturals

Photo by the Linda Edit.



Oxybenzone doesn’t just affect you because if you’re pregnant it can impact the health of your baby too. Studies have shown significant relations between oxybenzone exposure in pregnant women, shorter pregnancy terms and lower birth weights in newborn males. A study conducted by American Academy of Pediatrics in 2006 found that infants with moderately low birth weights were significantly more likely to have a special health care need, chronic condition (diabetes, heart disease, etc), learning disability, and/or attention-deficit disorder (ADD) or attention-deficit/hyperactivity disorder(ADHD).

Oxybenzone not only affects your baby during pregnancy but can continue to affect them after they are born through breast milk. Margaret Schlumpf of the University of Zurich detected oxybenzone in Swiss women’s breast milk, which suggests that newborns may be exposed to these substances (Schlumpf 2008, Schlumpf 2010).



In a study conducted on American children, researchers found that adolescent boys with higher oxybenzone measurements had significantly lower testosterone levels (Scinicariello 2016). Lower levels of testosterone has been linked to low energy levels, hair loss/male pattern balding, increased body fat, and lowered sex drive.


oxybenzone and coral reefs sunscreen - kaia naturals

Photo by Catrin Johnson.



When we swim in the ocean with chemical sunscreen on, oxybenzone enters into the water and gets ingested by corals. Oxybenzone has been found to decrease the coral’s defenses against bleaching and disrupts it’s reproduction and growth cycles.

In 2018, Hawaii passed a bill banning sunscreens containing the chemicals oxybenzone and octinoxate in efforts to help protect their marine life and coral reefs.



The FDA says the only sunscreen ingredients that they know for certain are safe are zinc oxide and titanium dioxide, also known as the two main active ingredients found in mineral sunscreens. They work by sitting on top of the skin and reflecting the sun’s rays. Mineral sunscreens that use zinc oxide or titanium dioxide are also coral-reef safe, as their particle sizes are much bigger than oxybenzone and cannot be ingested by corals.

Because mineral sunscreen doesn’t penetrate the skin, its only real downside is the trademark white cast sunscreen is famous for. But hey, I’d rather look like a ghost on the beach knowing my skin is protected.



Look for tinted mineral sunscreens or apply sunscreen underneath your makeup.


A lot of natural sunscreens use coconut oil which can leave your skin looking and feeling greasy. It’s also not ideal to use coconut oil on acne-prone skin as it can clog your pores, so look for coconut oil-free natural sunscreens.


Do you have a favourite mineral sunscreen? Share your recommendations below!