What your clothes are actually made of

What the fiber line actually tells you

Four things, roughly, and none of them are printed anywhere else on the garment.

• Heat and moisture. Some fibers absorb water into the fiber itself. Others repel it and move it along the surface, or hold it against the body. This single property explains most of how a fabric feels after twenty minutes of wear.
• How it ages. Pilling and color fading are the top two measured causes of garment failure, according to a UK WRAP/Defra survey analyzed in the Journal of Cleaner Production in 2022. Both are largely written into the textile before you hand over your card.
• What goes into the wash water. Polyester, nylon and acrylic shed plastic microfibers when laundered. Cotton, wool and linen shed too, but what they shed is not plastic.
• The chemistry it is likely to carry. Finishes never appear on a care label, but certain fibers and certain marketing promises travel together. A fabric that resists stains, creases or odor is usually doing so with something applied to it.

Read the fiber line first, then the price.

How to read a blend

Fiber content is legally required in both the US, under FTC textile rules, and the EU, under the Textile Regulation, and it is listed in descending order by weight. The first fiber named is the largest share. That ordering is information, not formatting.

Two labels, both of which a shop will happily call cotton:

• 95% cotton, 5% elastane. This is a cotton garment with a recovery thread running through it. It feels like cotton, breathes like cotton and ages like cotton. The elastane is doing one narrow job: pulling the fabric back to shape after it stretches, at the cuff, the waistband, the knee.
• 52% cotton, 48% polyester. Nearly half of this garment is plastic. It will not behave like cotton. It handles heat and moisture somewhere between the two families, holds its shape better, creases less, dries faster, and sits warmer against skin during a long wear.

So the useful habit is to read the first number for what the fabric essentially is, and the small numbers for what jobs someone asked it to perform. A few percent of elastane changes how a garment moves. Twenty percent changes what the garment is for.

Natural fibers: cotton, wool, linen, silk, cashmere

These come from a plant or an animal and arrive at the loom with their structure broadly intact. What they share is a working relationship with water. The fiber absorbs moisture rather than repelling it, which is why natural fabrics tend to feel cooler and drier against warm skin, and why they generally take longer to dry on a line.

Past that, they diverge more than people expect.

• Cotton is absorbent and soft, holds moisture once it has taken it on, and is the fiber shoppers reliably pay a premium for. Remember that last part when you reach the accuracy section.
• Linen is a stiffer bast fiber, usually woven loosely, and it moves air. It creases, and the creasing is structural rather than a defect.
• Wool takes on moisture vapor while still feeling dry to the touch, and buffers temperature in both directions. Fiber diameter, not fiber type, decides whether it feels soft or prickly.
• Silk is a protein filament rather than a spun staple, which is where the smoothness and the sheen come from. It is more delicate in the wash than the price tag implies.
• Cashmere is wool's finer cousin from a different animal, soft because its fibers are thin enough to bend against skin, and priced accordingly.

Synthetic fibers: polyester, nylon, acrylic, elastane

These are plastics, extruded from petroleum-derived polymers and spun into filament. As a family they do not absorb water into the fiber. That one property explains most of what people like about them and most of what they complain about: synthetics dry quickly, hold color and shape, resist creasing, cost less to make, and they trap heat and moisture against the body when worn tight or worn for a long stretch.

• Polyester is the default synthetic and the most common fiber in the world's wardrobes. Strong, cheap, colorfast, non-absorbent.
• Nylon is the tougher one, better against abrasion, and it holds its surface longer than polyester in the same knit, so it resists pilling better in garments that see repeated friction. Two synthetics in the same price bracket, visibly different aging.
• Acrylic is the wool substitute, engineered for loft and warmth at a much lower cost. The substitution shows up in how the surface holds up.
• Elastane is never the whole garment. It appears in small shares and does exactly one thing, which is return the fabric to its original dimensions. You will also see it labeled spandex.

Two practical notes. Synthetics are where testing keeps finding finishes and residues, which is covered in what a sports bra taught us about polyester. And synthetics are the source of the microfiber shedding described in one load of laundry, 700,000 plastic fibers.

Semi-synthetic fibers: viscose, modal, lyocell

Viscose sits between the two families and causes more confusion than every other fiber in this guide combined. It starts as plant cellulose, usually wood pulp or bamboo, which is then chemically dissolved and re-spun into fiber. The raw material is natural. The fiber is manufactured.

Behaviorally it borrows from both sides: it absorbs moisture much like cotton, drapes closer to silk, and is notably weaker when wet. You will see it labeled viscose or rayon depending on the market the garment was sold into, and modal and lyocell are close relatives produced by different processes. Because the fiber is made rather than harvested, the chemistry of the process matters as much as the plant it started as.

Why blends exist at all

Blending is not a trick played on shoppers. It is how a mill solves a problem it could not solve with one fiber:

• Stretch and recovery. Cotton does not spring back. A few percent of elastane means the knee of a pair of jeans does not stay bagged out at 4pm.
• Shape and crease resistance. Polyester blended into cotton keeps a shirt looking pressed. That is why a blend often replaces a chemical wrinkle-resistant finish, which is its own tradeoff, covered in why your wrinkle-free shirt never creases.
• Cost. Polyester is cheaper than cotton, and blending is the most direct lever a manufacturer has on the shelf price.
• Drape and hand. Viscose added to a wool or a synthetic changes how a fabric falls and how it feels between two fingers.
• Durability at stress points. Nylon in a heel, a seat, an elbow.

The fiber line is where all of those tradeoffs are written down, in order, by weight. A blend is often the right garment. It is just a garment whose label is making more claims at once.

Blends are also where the label is least reliable

This is the caveat that makes the rest of this guide worth reading carefully.

An EU market-surveillance campaign known as JACOP published results in June 2026 after inspectors in eight countries tested 132 garments against their own labels. Overall, 37% were mislabeled. Blends of natural and man-made fibers failed 64% of the time. Claims of 100% of a single natural fiber failed 15% of the time. Authorities ordered 18 products withdrawn.

The earlier evidence points the same way. A Dutch government-commissioned study by Circle Economy, published in 2019, scanned more than 10,000 discarded garments with near-infrared technology and found fiber-content labels likely to mislead in 41% of cases. Cotton-polyester blend labels were accurate only about 23% of the time. Roughly a third of cotton-rich blends overstated their cotton content, while 11% understated the expensive fiber, meaning the garment was better than its label claimed. Discarded garments skew older than what is on the rack today, which is worth holding in view. The EU figures are current.

None of that argues against blends. It argues for reading a blend label as a claim with worse odds than a single-fiber one, and it explains why. Precision is fragile. The more numbers a label states, the more places one of them can drift, and the drift has historically leaned toward the fiber people pay more for. There is more on this in why blended fabrics are mislabeled so often and in how often clothing labels are wrong. Where you buy shifts the odds as well: in the same EU campaign, online purchases failed at 46% against 36% in physical stores, which is covered in our look at label accuracy.

Two things partly close the gap. Finished-product certification is checkable: OEKO-TEX® Standard 100 and GOTS® both publish free databases where a certificate number either resolves or does not, and a logo with no number attached cannot be checked at all. And composition can be measured properly. The standard methods are the ISO 1833 series and AATCC 20 and 20A, which identify fibers and then determine percentages by dissolving one fiber out of a weighed sample and weighing what remains. Lynen commissions independent ISO 17025 accredited laboratories to run those tests and publishes what comes back, including the results that disagree with the tag. We do not operate a laboratory ourselves, we have not checked every garment, and where we have not checked, we say so.

Labels are also changing container. Under EU Ecodesign rules, garments sold in Europe are expected to carry a scannable digital product passport around 2027, with the detailed rules still being finalized. A passport is a brand-declared record, so it is the same claim in a better format. Independent measurement is what turns a claim into a fact.

Start with the fiber you are holding

• Cotton. Absorbent, soft, and the fiber most often overstated on a label.
• Wool. Temperature buffering, moisture handling, and why fiber diameter decides comfort.
• Linen. A loosely woven bast fiber built for airflow, creases included.
• Silk. A protein filament, smooth and light, more delicate than its price implies.
• Cashmere. Goat undercoat fine enough not to prickle, and a premium with a standing incentive to fake it.
• Polyester. The default synthetic. What it does with heat, moisture, color and time.
• Nylon. The tougher synthetic, and the places it outperforms polyester.
• Acrylic. The wool substitute, and what the substitution costs you.
• Elastane. Small share, single job. Also labeled spandex.
• Viscose. Plant cellulose, manufactured into fiber. Also labeled rayon.
• Modal. Viscose's softer, stronger-when-wet relative, living where softness matters.
• Lyocell. Closed-loop regenerated cellulose, strong wet and unusually good with moisture.

So what fabric is best

The useful answer arrives once you name the job, and matching fiber to the job has a page of its own: the hottest day, hard wear, skin that reacts easily, and the limits of what a fiber name can promise. What the fiber line can do today is tell you what you are actually buying, provided the line is accurate, which is the reason this guide has a caveat section and the reason we send garments to a lab instead of taking the tag at its word.