I'm sorry, but someone had to tell you.
Your armpits and your groin have the same type of sweat gland. Not the regular kind that cools you down when you go for a run. The other kind. The smelly kind.
Once I learned this, I couldn't stop thinking about it. We put so much thought into what goes on our armpits. Deodorant. Breathable fabrics. Antiperspirant if you're fancy. And then we wrap our groin in polyester and wonder why things get a bit... warm.
Let me explain what's actually going on down there.
Two types of sweat glands
Your body has two main types of sweat glands.
Eccrine glands are everywhere. They make the watery sweat that cools you down. Mostly harmless, mostly odourless.
Apocrine glands are different. They're concentrated in a few spots: your armpits, your groin, and around your nipples. They kick in at puberty, and they make a thicker sweat that ramps up when you're stressed, anxious or hot.
So when you're nervous in a meeting and feel it in your armpits? Your groin is feeling it too. It's just quieter about it.
Here's the twist: sweat doesn't smell
Fresh apocrine sweat is actually odourless. Wild, right?
The smell happens when the bacteria that naturally live on your skin start breaking that sweat down. More moisture plus more warmth equals more bacteria having a party.
Which brings me to your undies.
Synthetic undies are a bacteria spa (and cotton isn't much better)
Most undies are made from synthetic fabrics like polyester and nylon. They're cheap, stretchy and look nice on the shelf.
But synthetic fabric doesn't absorb moisture well. It traps it against your skin, and research has found odour-causing bacteria love polyester. It holds onto smell in a way natural fibres don't.
"Fine," you say. "I'll just wear cotton."
Cotton is better, but it can't keep up either. It soaks up moisture, then sits there wet against your skin. It's slow to dry, so once it's damp, it stays damp. And damp and warm is exactly what bacteria are looking for. Anyone who's worn a cotton t-shirt on a hot day knows the clammy feeling I'm talking about.
So whether it's synthetic or cotton, you've got your armpit-style sweat glands working overtime, and a fabric that isn't built to handle it. Then you add discharge.
And then there's discharge
Healthy discharge is normal. Most of us produce a bit every single day, and it's your body doing its job.
It's also acidic. Think of it as vinegar's milder cousin. That acidity keeps the bad bacteria out, which is great for you and terrible for dark undies. It's why so many of us end up with faded, bleached-looking patches in the gusset.
That isn't you being gross. That's your body being clever, and your undies not keeping up.
Why I line my gussets with merino
This is exactly why I made Luckies.
Every pair has a merino-lined gusset, and merino is honestly a bit of a show-off when it comes to moisture.
- It soaks up moisture without feeling wet. Merino absorbs moisture into the fibre itself, holding around 30% of its own weight before it even feels damp. Cotton feels wet long before that. Synthetics barely absorb at all.
- It's naturally odour-resistant. Merino holds onto smell far less than synthetics. It's why hikers wear merino base layers for days on end.
- It breathes. It helps regulate temperature, so you're not stewing.
And because my gussets are patterned, any fading from discharge just blends in. No more ruined pairs.
The bottom line
Your body isn't the problem. It's doing exactly what it's designed to do.
Your undies just need to keep up.
If you'd never wear a plastic bag on your armpits, maybe it's time to stop wearing one on your crotch. 😉