Polyester And Skin Irritation
If you chafe every session, you have probably assumed it is you. Your gait, your weight, the heat, the distance.
It is usually the fabric.
Three things happening at once.
Irritation from synthetic kit is rarely one cause. It is heat, friction and moisture arriving together, and polyester makes all three worse.
Heat with nowhere to go
Polyester is dense and non-porous. It pushes sweat to the surface and holds warmth against the skin underneath. Skin held warm and damp for an hour has a compromised barrier before any rubbing starts.
Moisture on the surface
The fibre cannot absorb, so the sweat sits between the fabric and you. Wet skin under friction breaks down far faster than dry skin does. That is the mechanism behind most chafe.
A surface that grips
Synthetic mesh liners are engineered to hold position. Held against wet, warm skin for an hour, that is friction applied to the exact place you least want it.
It is not a reaction to wool. It is a reaction to plastic.
Plenty of men who assume they are sensitive to fabric have only ever tested that assumption against synthetics and coarse wool. Two things that both irritate skin, for completely different reasons.
In a randomised clinical trial of 39 children with mild to moderate eczema, superfine merino worn against the skin for six weeks reduced severity compared with cotton, and the improvement reversed when they switched back.
Superfine specifically. Coarse wool above roughly 30 micron is a different fibre with a different effect, and it is where the itchy jumper reputation comes from.
The number that decides whether wool itches
Prickle is mechanical, not an allergy. It correlates with the percentage of fibres coarser than about 30 micron. Ours sits at 17.5.
Source: Naylor, Stanton and Speijers, Textile Research Journal, 2014.
Nero merino liner short
Merino next to skin, organic cotton outside, and no separate underwear needed.
All natural fabrics
Regulates temperature
Absorbs and evaporates
Soft as cashmere
New Zealand merino
The liner is the layer to change.
It sits against the exact skin that chafes, for the whole session, and it is synthetic mesh on almost every pair of shorts sold. Changing the shell does nothing if the liner stays the same.
No polyester. No nylon. No plastic anywhere it touches you.
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The material is next-level, breathable, soft, and somehow manages to feel both lightweight and durable at the same time. The fit is perfect, relaxed but sharp, and they move with you without ever feeling bulky or stiff.
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More: is polyester bad for your skin · chemicals in gym clothes · Eczema trial: Su et al, British Journal of Dermatology · Micron threshold: Naylor et al, 2014