One of the things that first drew us to Merino wool was something surprisingly simple: you can wear it for a remarkably long time before it starts to smell.

If you've ever worn a synthetic running top for a hard session, you'll probably know the alternative. It can smell fine when you put it on, decidedly less fine when you take it off, and sometimes somehow worse again when you pull it out of the washing basket.

Merino behaves very differently.

It isn't magic, and Merino certainly can eventually smell. But wool has some unusual properties that mean it generally holds on to far less body odour than many synthetic fabrics.

So what's actually going on?

Why doesn't Merino wool smell as quickly?

Sweat itself isn't usually the main culprit behind body odour. The familiar smell develops as microorganisms on our skin interact with compounds in sweat and skin secretions.

Your clothing then becomes part of the equation.

Merino wool is hygroscopic, which basically means the fibre can absorb moisture vapour from the environment around it. Rather than moisture simply sitting at the surface of the fabric, wool can take a surprising amount of it into the structure of the fibre.

Wool fibres can also absorb and hold some of the volatile compounds associated with odour.

The practical result is something anyone who has spent several days in the same Merino top will recognise: it stays wearable for much longer than you might expect.

Merino wool vs polyester

This isn't just something wool companies like to say.

Research comparing wool, cotton and polyester fabrics after they had actually been worn found a strong relationship between fibre type and odour. Polyester produced the highest odour intensity, while wool and cotton were considerably lower.

Other research looking at wool and polyester blends has found that introducing wool can reduce perceived body odour compared with 100% polyester.

That's particularly relevant to outdoor clothing.

Synthetic fabrics can be excellent at moving liquid sweat and drying quickly. But if you've ever taken a couple of polyester running tops away for several days, you'll know that odour can become a problem surprisingly quickly.

Merino gives you a different balance.

Is Merino wool antibacterial?

You'll often hear Merino described as "naturally antibacterial".

We think odour resistant is a better description.

Research suggests the difference in smell between wool and polyester isn't simply explained by there being fewer bacteria on wool. The way the fibre manages moisture and interacts with odour-producing compounds appears to be an important part of the story.

So Merino doesn't need to sterilise itself to stay fresher for longer.

Does Merino wool smell when wet?

Not necessarily. In our experience, our Merino clothing doesn't develop the traditional "wet wool" smell people sometimes associate with heavier wool garments.

Modern superfine Merino is a very different proposition from the thick wool jumpers many of us grew up with. The fibres are much finer, and the finished fabrics are lightweight and designed to be worn next to the skin.

More importantly, getting wet doesn't suddenly remove Merino's odour-resistant properties. Whether you're sweating on a climb or caught out in the rain, one of the reasons we use Merino is that it remains remarkably pleasant to wear.

Can Merino wool smell after washing?

A properly washed and dried Merino garment shouldn't routinely smell unpleasant after washing.

As with any clothing, problems can occur if a garment is left damp for a long period, stored before it is completely dry, or picks up odours from the washing machine itself. Following the garment's care instructions and allowing it to dry properly should avoid this.

One of Merino's advantages is actually that it generally needs washing less frequently than many synthetic garments.

If it still looks clean and smells fresh, there's often no reason to wash it simply because you've worn it once.

Why this matters outdoors

Odour resistance can sound like a fairly minor benefit until you actually need it.

For a Sunday morning run, it might just mean your top doesn't immediately need to go into the wash.

For a multi-day hike, bikepacking trip or week away with limited luggage, it becomes much more useful.

One Merino T-shirt can be worn repeatedly rather than packing a clean synthetic top for every day. That means less kit, fewer washes and clothing that's easier to live with when you're away from home.

It's also one of the reasons Merino works so well for travel.

Why we use Merino at Manumit

This was one of the characteristics that made us want to build Manumit around Merino in the first place.

Our 100% Merino Wool T-Shirts use superfine 17.5 micron Merino at around 150 gsm. They're designed to work as everyday T-shirts as well as technical layers for running, hiking, climbing and travelling.

We've also taken Merino beyond the T-shirt.

Our Trail Sun Hoody uses Nuyarn®, combining 70% New Zealand Merino with 30% nylon to create a lightweight technical layer with the comfort and odour resistance we want from wool, alongside additional durability.

Neither garment is immune to getting dirty or smelling forever.

But that's rather missing the point.

The advantage of Merino is how long it takes before you feel the need to wash it.

And once you've spent a few days living in the same top, that's quite difficult to give up.