Merino or polyester for running.
Polyester dominates running apparel for good reasons. Here is where merino beats it, where it does not, and how to choose for the session in front of you.
Most running kit is plastic. Polyester, nylon and elastane are petroleum derived, and they make up the overwhelming majority of what is sold as technical apparel. They are cheap, strong and quick to dry, which is why the industry settled on them.
Merino is a different proposition. Here is how the two compare on the things that actually matter over distance.
Odour
This is the clearest difference, and the one most runners notice first.
Polyester holds odour. The fibre is hydrophobic, so sweat sits on the surface rather than being absorbed, and the bacteria responsible for odour feed on what is left behind. The smell builds over repeat wears and often survives washing.
Merino absorbs moisture into the fibre itself, away from the skin surface, which gives odour causing bacteria less to work with. In practice a merino tee can be worn several times between washes without turning. That is why it has a following among travellers and multi day runners.
Temperature
Merino works across a wider range. Polyester is better at one thing.
Polyester wicks quickly and dries fast, which is genuinely useful in hard, hot efforts. What it does not do is buffer. It cools you as fast as it dries, which is why a polyester shirt turns cold the moment you stop.
Merino regulates. It absorbs moisture vapour before it becomes liquid sweat, and releases heat as it does so. The practical result is a garment that feels warm as conditions cool and breathable as they warm. For long runs with changing weather, or the stretch between finishing and getting home, that range matters more than raw drying speed.
Next to skin feel
Micron is the number to look for.
Wool has a reputation for itch that comes from coarse fibres used in older garments. Fibre diameter is measured in microns, and anything at or below about 18.5 is generally comfortable directly against skin. Our merino is 17.5 micron.
Polyester is smooth but non absorbent, which is why it can feel clammy once you are properly sweating.
Microplastics
Synthetic fabrics shed. Wool does not.
Every wash of a synthetic garment releases microscopic plastic fibres, and research suggests wear releases them too. The scale is still being quantified and the health picture is still emerging, so we are careful about how far we take that claim. What is not in dispute is the source: if the fabric is plastic, the shedding is plastic.
Wool is a protein fibre and biodegrades at end of life.
Durability and cost
Polyester wins on both. This is the honest trade.
Polyester is stronger, more abrasion resistant and considerably cheaper to produce. A merino garment costs more and needs a gentler wash: cold, wool cycle, dried flat.
If the only criteria are price and lifespan, polyester is the rational choice. We think the other criteria matter.
Which to choose
Natural fibre. Every time.
Polyester is cheaper and it lasts longer. Those are the only two arguments for it, and both are arguments for the manufacturer rather than for you.
Everything you actually feel goes the other way. Merino handles temperature across a range instead of a point. It stays fresh across repeat wears instead of holding odour through the wash. It sits comfortably against skin at fine micron counts instead of turning clammy. And when it reaches the end of its life it biodegrades, because it is a protein fibre rather than a plastic one.
A polyester garment sheds microscopic plastic every time it is washed and worn, and those fibres do not go anywhere. Ours are the only clothes most people own that they wear directly against their skin for hours at a time, through heat and sweat. We do not think that should be plastic.
That is why we build in natural fibre and nothing else. Not as a compromise, and not as a premium option alongside a synthetic line. It is the whole point.
Common questions
Is merino or polyester better for running?
Merino. It regulates temperature across a range rather than a point, resists odour across repeat wears, sits comfortably against skin at fine micron counts, and biodegrades at end of life. Polyester is cheaper and more durable, and it sheds microplastics every time it is washed and worn.
Does merino wool smell less than polyester?
Yes. Merino absorbs moisture into the fibre rather than leaving it on the surface, which gives odour causing bacteria less to feed on. Polyester is hydrophobic, so sweat sits on the surface and odour builds over repeat wears.
Is merino wool itchy against the skin?
Not at fine micron counts. Fibre diameter is measured in microns and anything at or below roughly 18.5 micron is generally comfortable next to skin. Enduro merino is 17.5 micron.
Does polyester shed microplastics?
Yes. Synthetic fabrics release microscopic plastic fibres during washing, and research indicates wear releases them too. Wool is a protein fibre and biodegrades at end of life.
Is polyester more durable than merino?
Yes. Polyester is stronger, more abrasion resistant and cheaper to produce. Merino costs more and asks for a gentler wash.