💡 Quick Answer: Why use merino wool in period underwear

Merino wool is particularly well-suited for period underwear because it combines next-to-skin softness with natural moisture, odour control, and temperature regulation. In joni Leakproof Underwear, a premium 100% merino wool lining sits against the skin, while the layers underneath handle absorption and leak protection.

Merino wool. You probably never thought about it for period underwear.

But when we set out to create joni Leakproof Underwear, we weren't interested in making another version of what was already out there. We wanted to rethink period underwear from the layer closest to your body out.

And that led us somewhere unexpected: merino wool.

It's soft. Breathable. Naturally helps manage moisture, temperature, and odour. There's a reason merino is prized as a premium performance fabric in clothing designed to be worn next to the skin for hours at a time.

So we had a question: If merino can make performance clothing better, why not period underwear? Turns out, it makes a whole lot of sense.

New to reusable period care? Start with our Complete Guide to Leakproof Period Underwear.

Why is merino wool good for period underwear?

Period underwear has a big job: absorb menstrual flow and help prevent leaks. But when we design period care products at joni, we look at the bigger picture and wonder how we can make things better. We asked, how can we bring innovation to the period underwear space?

In addition to designing underwear that actually feels good to wear, we thought about what happens during the course of a day: moisture, warmth, movement, and menstrual fluid.

That's why we became a little obsessed with the lining.

For joni Leakproof Underwear, we chose a premium 100% merino wool jersey for the layer sitting directly against your body.

Not because merino sounds fancy, but because it performs.

Merino is nature's performance fabric

There’s a reason merino is a favourite in high-performance clothing. Best known as a go-to fabric for outdoor gear, it works hard behind the scenes—managing moisture, odour, and temperature while staying soft against the skin.

Those same qualities that make merino such a performance powerhouse outdoors make an incredible amount of sense in period underwear, too. We just gave it a new assignment.

Does merino wool help manage moisture?

Yes—and this might be one of its most interesting qualities for period underwear.

Wool can absorb a significant amount of moisture, absorbing up to 30% of its own weight before feeling wet.

Why does that matter?

Period underwear needs to handle menstrual fluid, but comfort isn't only about how much the absorbent core can hold. It's also about what it feels like next to your skin while it's doing it.

The merino lining works as part of a larger system: the lining helps manage the next-to-skin environment while the absorbent layers underneath capture and hold menstrual fluid.

Absorbency matters. How you feel while your underwear is absorbing matters, too.

Want to know what's happening underneath the merino? Read How Does Period Underwear Work? for a closer look at absorbency, layers, and leak protection.

Does merino wool help with odour?

Just to be clear: period smells are normal. Worrying about them all day doesn’t have to be.

And guess what? Merino wool helps here, too. By absorbing moisture, it helps manage the damp environment where odour-causing bacteria can thrive—naturally helping keep odours in check.

That means the fibre itself is doing some pretty impressive work.

No big fuss.

Just really smart material.

Is merino wool breathable?

Merino is a natural fibre well-suited to clothing worn close to the body, which is one reason it has become such a favourite in performance apparel.

But in period underwear, breathability is about more than comfort.

Period underwear is designed to manage fluid for hours at a time. Add body heat and limited airflow, and you can create a warm, damp environment—the exact opposite of what you want next to sensitive skin.

Breathable materials allow air to circulate and help manage moisture rather than trapping it against the body. That can help reduce the prolonged dampness that may contribute to discomfort and irritation.

Because while stopping leaks is the immediate job of period underwear, supporting menstrual health matters, too.

That’s another reason we chose merino. Its natural moisture-management and temperature-regulating properties help create a more comfortable next-to-skin environment while the absorbent layers underneath get to work.

Great period underwear shouldn’t just keep your clothes dry. It should consider the skin underneath, too.

Does merino wool regulate temperature?

This one surprises people.

Wool doesn't automatically mean warm.

Merino is valued as a performance fibre because it helps manage the environment next to your skin across changing conditions, making the natural properties of merino suitable to wear across different seasons and locations.

That's pretty useful for something you're going to wear for hours at a time.

The goal isn't to make your underwear warmer.

It's to help keep you comfortable.

But isn't wool itchy?

We knew you were going to ask.

When many of us hear "wool," we picture a scratchy sweater.

This is not that wool.

Merino fibres can be much finer than the coarse wool you might associate with an old winter sweater. The extra-fine merino wool we use is specifically chosen for its "next-to-skin comfort" range, including fine single-jersey fabrics.

That's an important distinction.

Fine merino can be made into soft, lightweight fabrics designed to sit comfortably against the body.

So no, we didn't put sweater material in your underwear.

We chose merino because next-to-skin comfort is one of the things it does exceptionally well.

Why does the lining of period underwear matter?

When people compare period underwear, they usually start with one question: How much does it hold?

It's a good question. joni Leakproof Underwear absorbs up to 40 mL—about four regular tampons.

But we think there's another question worth asking: What's touching my skin while it's doing that?

Period underwear is a system, and every layer has a different job.

The absorbent core needs to capture and hold menstrual fluid. The leak-resistant barrier needs to help stop fluid from reaching your clothes. And the lining? That's the part you actually feel. So we gave that job to a premium performance fibre.

For us, that was the lightbulb moment. Period underwear deserves performance materials, too.

What makes joni's merino wool period underwear different?

We think premium period underwear should mean more than adding more layers, more bulk, or more features.

It should mean choosing better materials and engineering them to work together.

That's exactly what we did.

Premium merino wool lining: 100% merino wool sits next to your skin, helping naturally manage moisture, odour, and temperature.

Ultra-thin absorbent core: Absorbs up to 40 mL—about four regular tampons—without unnecessary bulk.

360° leak protection: A full front-to-back leak shield provides added protection beyond the central absorbent area.

Soft lyocell and cotton body: Stretchy, comfortable, and designed to feel like the underwear you already love wearing.

100+ washes: Validated through wash-cycle testing so you can wear it again. And again. And again.

The technology doesn't need to feel technical. Ideally, you barely notice it at all.

Is merino wool a sustainable material?

Merino gives us another reason to get excited: it's a natural, renewable fibre.

Sheep grow a new fleece after they're shorn, making wool renewable, and wool is also biodegradable under the right conditions.

For us, that's a bonus to the performance story—not a reason to compromise on it.

Because the first question we ask about a material is always:

Does it make the product better?

With merino, the answer was yes.

Premium material. Specialist expertise.

Not all merino is the same—and when you're putting it next to some of the most sensitive skin on your body, sourcing matters.

The merino used in joni Leakproof Underwear is Australian merino sourced through a specialist merino textile manufacturer with deep expertise in performance fabrics. The company is a Woolmark licensee and produces merino textiles for sports, outdoor, active leisure, and other performance applications.

In other words, we didn't just choose merino. We chose people who really know merino.

Why don't all period underwear brands use merino wool?

Period underwear can be made from many different materials, and brands make different choices about construction, performance, cost, and feel.

Merino is a premium material. And choosing it for the lining means treating that next-to-skin layer as a performance component—not simply another piece of fabric.

For joni, that was worth it.

We weren't looking for the most obvious material. We were looking for the right material for the job.

Once you understand what merino brings to period underwear—moisture management, odour management, temperature regulation, and soft next-to-skin comfort—it doesn't seem like such an unusual choice. It feels like an obvious choice.

This is a difference you can feel

You can compare absorbency numbers. You can count layers. You can read every technical spec on the page. But period underwear ultimately has to live on your body.

And that's why we're so excited about merino.

It's not a novelty. It's not there because it sounds premium. It is premium because of what it does.

Breathable next-to-skin comfort. Natural moisture, odour, and temperature management. Serious absorbency and leak protection working underneath.

Once you try period underwear designed this way, you might start wondering why it wasn't made this way all along.

Feel the difference. Meet joni Leakproof Underwear →

Looking for the bigger picture? Explore our Complete Guide to Leakproof Period Underwear, or learn How Period Underwear Works.