The chemical finishes on your clothes, and what washing removes

The fiber label tells you what a garment is made of. It doesn’t tell you what was put on it afterward. Mills use around 1,900 chemical substances to make textiles, and 165 of them carry an EU hazard classification. Some wash out at the mill. A lot of the finishing chemistry is designed to stay in the fabric when you buy it.

How finishes get onto fabric

Most finishes are padded on: the fabric runs through a bath of finishing liquor and between rollers, then it’s dried and baked so the finish sets. That’s how finishing liquor is applied in more than 80% of cases, according to the EU’s technical reference for textile mills, and it notes that a final wash “tends to be avoided unless absolutely necessary.” Softeners, increasingly silicone ones, are padded or sprayed on the same way, which transfers all of the liquid onto the fabric.

Finish	Words on the label	What it’s made of	Does washing remove it?
Wrinkle-free	Non-iron, wrinkle-free, durable press, easy care	Resins built from urea, melamine, glyoxal or formaldehyde	Loose formaldehyde mostly washes out; the resin stays
Water-repellent	Water-repellent, DWR, weatherproof	Fluorinated polymers (PFAS), silicones or hydrocarbon waxes	It wears off slowly, and fluorinated ones shed PFAS as they go
Stain-resistant	Stain-resistant, stain-release, oil-repellent	Fluorinated finishes, the only kind that repels oil	Built to last
Odor control	Antimicrobial, anti-odor, odor control, silver	Silver, triclosan, quaternary ammonium compounds	Half or more of some agents is gone after 10 washes
Flame-resistant	Flame resistant (children’s sleepwear)	Durable flame retardants bonded to the fiber, or flame-resistant fiber	Required to survive 50 washes

Wrinkle-free and no-iron

No-iron shirts are cotton cross-linked with resins made from urea, melamine, glyoxal or formaldehyde, and those resins can release formaldehyde. When the US Government Accountability Office tested 180 skin-contact items in 2010, 10 were over the strictest international limits, and more than half of those were labeled durable press. The US has no legal limit on formaldehyde in clothing, and labels don’t say whether a garment was treated with it.

Formaldehyde is classified by IARC as carcinogenic to humans. On skin the concern is allergy, though dermatologists disagree about how often modern finishes cause it. For the full picture, see whether cotton is sustainable.

Water repellents (DWR)

A durable water repellent, or DWR, is what makes rain bead on a jacket. There are four kinds: side-chain fluorinated polymers, which are PFAS, silicones, hydrocarbon waxes, and newer chemistries such as dendrimers. Fluorinated DWRs come in long-chain (C8) and short-chain (C6) versions.

Fluorinated DWR doesn’t stay put. When 13 commercial DWR garments were weathered for 300 hours to mimic their lifetime of use, the levels of some PFAS rose 5- to more than 100-fold in most of them. Washing sheds fibers carrying the fluorinated coating, and aging plus washing releases PFAS from both C6 and C8 finishes. Spray-on reproofers are another source: PFAS turned up in 60% of the impregnating sprays tested in one Swiss survey.

Fluorine isn’t needed to keep rain out. The best fluorine-free DWRs repelled water as well as short-chain fluorinated finishes in independent tests, and researchers called PFAS on everyday outdoor clothing “over-engineering.” What fluorine-free finishes can’t do is repel oil. See PFAS in clothing.

Stain resistance

Stain-resistant clothing and fabric is where the oil repellency comes in, and only fluorinated finishes provide it. In a 2022 investigation, 72% of products marketed as stain- or water-resistant contained PFAS, while none of the tested products without those claims did.

Odor control

Antimicrobial finishes are sold as odor control, mostly on sportswear and socks. The common agents are silver, triclosan and quaternary ammonium compounds. They wash out: in Swedish tests, about half or more of the triclosan and triclocarban in treated textiles was gone after ten washes, and between 1% and 45% of a fabric’s silver came out in a single wash in another study. Many don’t work anyway. Of the antibacterial garments the Swedish Chemicals Agency tested, 68% had no effect after 10 washes and 28% had none before the first.

The odor problem is mostly a synthetic one. Polyester shirts worn to a workout smelled more intense and less pleasant than cotton, and odor bacteria grew almost only on the polyester.

Flame retardants in children’s sleepwear

US children’s sleepwear from nine months to size 14 must pass a flame test, as made and after 50 washes, unless it’s tight-fitting. Snug pajamas carry a yellow hangtag that says the garment isn’t flame resistant. Flame-resistant pajamas are made from inherently flame-resistant fabric or treated with flame retardants.

The rule has a history. In 1977 the Consumer Product Safety Commission banned children’s clothing treated with the flame retardant Tris, saying it could be absorbed through the skin or by mouthing. About 18 million treated garments were on sale. Polyester, acetate and triacetate were the fabrics that most often needed it.

Should you wash new clothes before wearing them?

Yes. In a 2022 study of 120 garments for pregnant women and young children, the 20 with the most formaldehyde were washed once on a quick cold cycle, and none had a detectable level afterward. The American Academy of Dermatology advises washing a child’s new clothes to remove excess dyes and fabric finishers.

Washing has limits. In clothing tested at Stockholm University, ten washes cut benzothiazoles by about half and quinolines by only a fifth, and quinolines were found mainly in polyester. Durable finishes are designed to stay: flame resistance has to survive 50 washes, and washing a fluorinated DWR can release more PFAS rather than less.

Fibers in this guide

• Cotton: not plastic
• Polyester: plastic