The most common misconception about clothing is that the fibre is the thing that matters. It is part of it — but a conventionally grown, heavily dyed, resin-treated cotton shirt is not obviously better than a plain undyed synthetic one.
What ends up against your skin is the fibre plus everything done to it: dyeing, finishing, and any performance treatment. This article covers the fibres. The finishes get their own article, because that is where most of the real exposure sits.
The short answer
Prefer natural or closed-loop fibres, look for OEKO-TEX or GOTS certification, and pay most attention to what sits against skin for long periods — underwear, base layers, sleepwear, and anything worn by a baby.
The natural fibres
Cotton
Breathable, soft, washable, and inexpensive. The default for good reason.
Conventional cotton is a pesticide-intensive crop, which is primarily an environmental and farm-worker issue rather than a residue-on-your-shirt one — processing removes most agricultural residue. Organic cotton is worth buying, but for accurate reasons rather than the implied one.
The more relevant question with cotton is what happened after the fibre stage, since cotton is the fibre most often given a wrinkle-resistant resin finish.
Linen
Flax needs far less water and pesticide than cotton, and it produces a durable, highly breathable fabric that improves with age. Excellent in heat.
It creases readily — which, as with sheets, is a reasonable sign nobody has treated it not to.
Wool
Thermoregulating, naturally odour-resistant, and naturally flame resistant. Merino is fine enough that most people who think they are “allergic to wool” can wear it comfortably — the itch from coarse wool is usually mechanical irritation rather than allergy.
Two things to check. Superwash or machine-washable wool has been treated, often with a resin coating, to stop it felting. And mulesing is an animal welfare issue in merino production — look for certified non-mulesed or ZQ certification.
Hemp
Grows quickly with minimal input, and produces an exceptionally strong fabric that softens considerably with wear. Often blended with cotton. A genuinely good option that is becoming easier to find.
Silk
Breathable, gentle on skin, and thermoregulating. Frequently treated though — watch for weighted silk, where metallic salts are added to increase heft, and note that most silk is dry-clean recommended, which brings its own chemistry.
The regenerated fibres
These start as plant cellulose and are chemically processed into fibre. The process matters enormously, and this is where the labels get confusing.
- Lyocell / Tencel — made in a closed-loop system that recovers and reuses the solvent. Soft, breathable, moisture-wicking. The one to look for.
- Modal — similar, generally better than viscose. Beech-derived, often produced to reasonable standards.
- Viscose / rayon — the older process, using carbon disulphide, which carries documented occupational health risks for textile workers. The finished garment is fine to wear; the concern is the making of it.
- “Bamboo” — almost always bamboo viscose. Soft and pleasant, with an environmental story considerably weaker than the marketing. Bamboo lyocell is the better version.
The synthetics
Polyester, nylon, acrylic, and elastane are petroleum-derived plastics. They are not a health emergency in a shirt, but they carry real trade-offs.
- Breathability. They trap heat and moisture, which is why synthetic clothing holds odour — bacteria thrive in that environment. This is the difference most people actually notice.
- Microplastic shedding. Every wash releases fibres into wastewater. A washing bag or filter reduces this substantially.
- Treatment likelihood. Synthetics are disproportionately given antimicrobial, water-repellent, and performance finishes — which is usually the more relevant concern than the polymer itself.
A small percentage of elastane in an otherwise natural garment is a reasonable trade for fit and durability. It is worth being pragmatic here.
Where dye actually matters
Certain azo dyes can break down into aromatic amines, some of which are restricted in many markets for exactly that reason. Reputable manufacturers and any OEKO-TEX certified fabric will have been tested against these limits.
Practical signals: deep saturated colours on cheap unbranded garments are the higher-risk case, dye that visibly transfers or bleeds heavily is a sign of poor fixation, and dark denim is a well-known culprit for crocking. Washing new clothes before wearing addresses most surface dye.
Where to focus
You do not need to overhaul a wardrobe. Prioritise by contact time and skin sensitivity.
- Highest: underwear, bras, base layers, sleepwear, socks, and anything for a baby or young child.
- Moderate: shirts, trousers, and anything worn against skin all day.
- Lowest: outerwear, jackets, and anything worn over other layers.
Buying less and buying better does more here than replacing everything you own, and secondhand clothing has the advantage of having been washed many times already.
Frequently asked questions
Should I wash new clothes before wearing them?
Yes. It is the easiest free improvement in this category. New garments carry loose dye, sizing agents, and processing residues from manufacturing and transit, and a single wash removes a meaningful share.
Is organic cotton worth paying more for?
For environmental and farm-worker reasons, genuinely yes. For residue on the finished garment, the difference is smaller than usually implied. GOTS certification is more meaningful than the word “organic” alone, because it also restricts dyes and finishes.
Are synthetic fabrics harmful to wear?
For most people, no. The practical downsides are breathability, odour retention, and microplastic shedding. Applied finishes on synthetics are usually the more relevant concern than the fibre.
What does “dry clean only” mean for exposure?
Traditional dry cleaning uses perchloroethylene, a solvent with recognised health concerns, and residue can remain in fabric. Air dry-cleaned items outside the bag before wearing, and look for wet cleaning or liquid CO2 cleaners where available.
Keep going
This is one section of the Non-Toxic Clothing Guide, which also covers what the certification labels mean and which finishes to avoid.