We've all experienced it.
You pull your favourite gym top out of the wash, convinced it's clean.
Then five minutes into your workout... that familiar smell is back.
It's one of the biggest frustrations with synthetic activewear, and the same thing can happen with synthetic underwear.
So why does it happen?
Sweat Isn't Actually What Smells
Here's something that surprises a lot of people:
Fresh sweat is mostly odourless.
The smell develops when naturally occurring bacteria on your skin break down components of your sweat. As they do, they produce compounds that create the body odour we recognise.
That's completely normal.
The question is: what happens to those bacteria and oils once they soak into your clothing?
Why Plastic-Based Fabrics Can Hold Onto Odours
Many gym tops, sports bras and underwear are made from synthetic fibres such as polyester, nylon and polyamide.
These materials are popular because they're lightweight, stretchy and often marketed as moisture-wicking.
But there's another side to the story.
Research suggests that synthetic fibres can retain body oils and odour-causing bacteria more readily than many natural fibres. Over time, those compounds can become harder to remove completely in a normal wash.
That's why a gym top can smell fresh in the wardrobe but develop an odour almost as soon as it warms up during exercise.
Sound familiar?
It's Not Just Your Gym Top
The same principle applies to your underwear.
During a busy day, a workout or a heatwave, your underwear is exposed to warmth, moisture and friction.
If it's made from synthetic materials, those fibres may retain odour-causing compounds more readily than natural fibres.
That's one reason many women choose cotton underwear for everyday comfort.
Why Cotton Feels Fresher
Cotton is a natural fibre that's known for being soft and breathable.
It allows air to circulate more freely and many people find it feels fresher throughout the day, particularly when compared with synthetic alternatives.
While no fabric can stop sweating completely, choosing breathable cotton underwear for women can help create a cooler, more comfortable environment next to your skin.
The Fabric You Wear Closest to Your Body Matters
We spend hundreds of pounds on skincare, deodorants and perfumes to help us feel fresh.
But what about the clothing that sits against our skin all day?
If you've ever wondered why your favourite synthetic gym top seems to hold onto odours no matter how many times you wash it, your underwear deserves the same consideration.
Choosing natural, breathable cotton is a simple change that can make a real difference to everyday comfort.
At Cotton Coup, we believe feeling fresh starts with your first layer.
Because if you've already upgraded your gym leggings, trainers and sports bra, maybe it's time to upgrade your underwear too.