Why Our Sheets Wrinkle, and Why That's a Good Sign
You know the moment. Fresh sheets out of the dryer, smoothed across the bed, and somehow they already look slept in.
Wrinkles in cotton sheets are what untreated cotton naturally does. Sheets sold as wrinkle-free, non-iron or easy care typically get that smoothness from a finish that locks the cotton fibers in place. Ours wrinkle because we leave that finish out.
Most of us read that as a flaw. Crisp means quality; creased means cheap. We rarely stop to ask what makes a sheet stay perfectly smooth in the first place.
What is a wrinkle, really?
Cotton is made of cellulose. Under pressure, heat and moisture, those fibers shift and settle into new positions, and the fabric holds the crease. Textile researchers describe this as an inherent property of cotton.
In other words, a wrinkle is not a defect. It is cotton behaving like cotton.
How do sheets become wrinkle-free?
To stop cotton from creasing, manufacturers can apply a crosslinking agent. It bonds the cellulose chains together so the fibers can no longer move freely, and the fabric springs back flat.
Same cotton, two different finishes
Untreated cotton
Fibers can shift and settle, so the fabric creases.
Crosslinked finish
Chains are bonded together, so the fabric springs back flat.
Simplified illustration. Based on Tekstilec (2018) and US Patent 5,447,537.
The most widely used of these agents is a resin called DMDHEU. A US patent for an alternative treatment notes that DMDHEU can release formaldehyde during processing, storage and consumer use. A 2010 US Government Accountability Office report confirms that formaldehyde can be used to enhance wrinkle resistance in textiles, especially cotton.
Why doesn't one wash take it out?
Because it is not meant to. Dermatologists have been pointing this out for years. In 2026, Cleveland Clinic dermatologist Dr. Shilpi Khetarpal noted that manufacturers sometimes add formaldehyde or other preservatives to new clothing to prevent wrinkling and mold, which can irritate skin. Dermatologist Dr. Jennifer Perryman has named bed sheets specifically among the textiles treated with formaldehyde resins, while noting that not every wrinkle-resistant item is treated.
As for washing it out, Dr. Jason Hadley of the Ogden Clinic explained in a widely shared 2018 interview that the resin is "designed to stick to our clothing." He added that one or two machine washes won't fully remove it.
1–2
Machine washes that, according to Dr. Hadley, won't fully remove a bonded resin finish.
2010
The year a US GAO report linked formaldehyde to wrinkle resistance in cotton textiles.
The same GAO report found that formaldehyde levels in the clothing it tested were generally low. The main concern it identified is allergic contact dermatitis, a form of eczema, in people who are sensitive. It also noted that avoiding treated textiles is hard, because labels do not say whether an item contains formaldehyde.
That is the real blind spot. Not that every smooth sheet is a problem, but that you usually cannot tell what made it smooth.
What we leave out
We can't tell you what is in any other brand's sheets. We can tell you what is in ours.
At AIZOME, formaldehyde and wrinkle-release resins are on our list of chemical classes we do not intentionally add, enforced by contract with every production partner. An independent laboratory, QTEC in Japan, tested our fabric for formaldehyde and recorded 0.00 detected. Our cotton also stays unbleached.
We are open about what we do use. Where a softer hand is needed, we apply only GOTS-approved or independently assessed finishing agents, in low residual amounts. You can see every step, and every certificate, on our Seed-to-Sheet™ page.
So when our sheets crease, nothing is holding the fibers still. That is the point.
A crisp sheet straight from the package tells you how it was finished. A soft crease tells you how it was made: cotton, left to be cotton.
What You Can Do: Read the Smoothness
- Treat "wrinkle-free", "non-iron" and "easy care" as signs that a finish was applied, then ask what it is.
- Ask the brand for test results. Labels don't disclose these finishes, so a lab report is the reliable way to know.
- Wash new bedding before use. It helps reduce dyes and irritants, though bonded finishes may not fully wash out in one or two cycles.
A different way to read a wrinkle
Next time you smooth out your bed, it might be worth asking what you'd rather have touching your skin all night.
FAQs
Are all wrinkle-free sheets treated with formaldehyde?
Not necessarily. Wrinkle-resistant treatments that do not release formaldehyde have been developed. Because labels don't disclose these finishes, the only reliable way to know is to ask the brand for test results.
Does washing new bedding help?
Dermatologists commonly recommend washing new textiles before use to reduce dyes and irritants. Finishes designed to bond with the fiber, however, may not fully wash out in one or two cycles. At AIZOME, we use no chemical finishes, so our bedding can be used straight out of the box.
Does wrinkling mean lower quality cotton?
No. Forming wrinkles under stress is a natural property of cotton fabric. Smoothness says more about the finish than the fiber.
Sources
- Cleveland Clinic Newsroom, "Should You Wash New Clothes Before Wearing Them?", March 2026. Link
- MDedge Dermatology, "Polyester. Plywood. Pizza. Skin allergens lurk in unusual places", July 2019. Link
- Great Bend Tribune, "Wash new clothes before wearing, dermatologist warns" (syndicated, c. 2018). Link
- US Government Accountability Office, "Formaldehyde in Textiles", GAO-10-875, August 2010. Link
- Tekstilec, "Performance of durable press finish on cotton with modified DMDHEU, citric acid, BTCA and maleic acid", December 2018. Link
- US Patent 5,447,537, "Cotton fabrics with improved strength retention". Link
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