Fabric School
Fabric School
What your underwear is actually made of.
A plain-language guide to the fabrics, certifications and care that decide how your underwear feels, how it wears and what went into making it.
Six fabrics, side by side.
Most underwear is made from one of these, or a blend. Here is how they compare on what matters next to your skin.
| Fabric | What it is | Against your skin | Chemical considerations |
|---|---|---|---|
| Organic cotton | Natural plant fiber grown without synthetic pesticides or fertilizers | Breathable and absorbent. Softens with washing. | Certification (GOTS) covers farming through finishing. This is what Puure uses. |
| Conventional cotton | Natural plant fiber grown with synthetic inputs | Same breathability and absorbency as organic | One of the most pesticide-intensive crops. Finishing chemicals are rarely disclosed. |
| Polyester & nylon | Petroleum-based synthetic fibers | Absorb little moisture, so in a snug fit they can hold heat and dampness against skin | Often given performance finishes. Shed plastic microfibers in the wash. |
| Modal & viscose (including “bamboo”) | Regenerated cellulose: plant pulp dissolved in chemicals and spun into fiber | Soft, drapey and absorbent | Depends on the mill. Look for certified processing, not just a plant name. |
| Lyocell (such as TENCEL™) | Regenerated cellulose made in a closed-loop process | Smooth, absorbent and breathable | Most of the solvent is captured and reused, which lowers its footprint. |
| Spandex (elastane) | Synthetic stretch fiber used in small percentages | Adds stretch and shape recovery | Synthetic. Puure keeps it to 5%. |
Why not 100% cotton?
Cotton is breathable, but it doesn’t stretch back. A small amount of spandex helps underwear keep its fit through a day of movement and many washes. We keep it to 5% and keep organic cotton as the main fiber.
“Every woman deserves to know what’s touching her body — and to trust that it’s safe.”Christina Phillips, Founder & CEO
Your questions, answered.
What’s the difference between organic and conventional cotton?
Organic cotton is grown without synthetic pesticides or synthetic fertilizers, which protects farmworkers, soil and water. The fiber feels the same. The difference is in how it is grown and, with GOTS, how it is processed.
Conventional cotton is one of the world’s most pesticide-intensive crops, and residues can persist in the fiber.
Is “organic” the same as GOTS-certified?
No. “Organic” on a label can mean different things unless a standard backs it up. GOTS, the Global Organic Textile Standard, is the leading standard for organic textiles. It covers the fiber and every step after it, including spinning, dyeing and finishing, with social criteria and annual third-party audits. Its highest label grade requires at least 95% certified-organic fibers.
GOTS vs. OEKO-TEX STANDARD 100: what’s the difference?
They answer different questions. GOTS certifies how organic fiber is grown and processed. OEKO-TEX STANDARD 100 tests the finished product for harmful substances, including certain azo dyes, formaldehyde, heavy metals and phthalates, whether or not the fiber is organic.
The strongest combination is both. Puure uses GOTS-certified organic cotton, with dyes tested against OEKO-TEX STANDARD 100.
What are modal, viscose and “bamboo” fabric?
They are all regenerated cellulose: plant pulp is dissolved in chemical solutions and spun into fiber. Most “bamboo” fabric is viscose. They can feel soft and silky, but the chemicals involved and how well a mill manages them vary widely, so the plant name on the label tells you very little.
Lyocell is a closed-loop version of the same idea that recovers most of its solvent.
Why does fabric matter for underwear specifically?
Polyester and nylon absorb very little moisture. In a snug garment worn for hours against skin that is already warm and damp, that can mean more heat and humidity held in place. Gynecologists commonly recommend breathable cotton, especially in the part that touches skin, as a simple precaution for comfort and irritation.
It is a precaution, not a cure. Fabric alone does not cause or prevent infections.
Should I wash new underwear before wearing it?
Yes, as a general habit. Washing removes loose fibers and handling residue from manufacturing and shipping. Follow the care label on your pair.
Organic cotton, up close
Certifications decoded.
“Your underwear has ingredients too. Do you know what’s in yours? We’ll wait…”
Labels are only as useful as the standard behind them. Here is what each one tells you, and what it doesn’t.
GOTS
Tells you
The fiber is certified organic and processing meets environmental and social criteria, with third-party audits.
Doesn’t replace
Testing of the finished garment for residues.
OEKO-TEX STANDARD 100
Tells you
The finished product was tested by an independent institute against a list of harmful substances at set limits.
Doesn’t tell you
That the fiber is organic or that the factory meets social criteria.
“Organic” alone
Tells you
Nothing you can verify without a certificate.
What to do
Ask for the certification and the certificate number.
“Natural,” “eco-friendly,” “sustainable”
Tells you
These are unregulated marketing terms. There is no standard behind them.
What to do
Look for a named, third-party certification instead.
GOTS certificates can be checked in the public database at global-standard.org. OEKO-TEX labels can be verified at oeko-tex.com.
“GOTS certified. OEKO-TEX approved. Third-party tested. This isn’t marketing; it’s documented, audited, and verifiable.”The Puure Standard
Care 101.
Good care keeps underwear soft and comfortable for longer, and it matters for sensitive skin too. These are general guidelines. Your pair’s care label always comes first.
- Check the care label. Follow the temperature and drying instructions for your pair.
- Use a fragrance-free detergent. Fragrances and dyes in detergent can irritate sensitive skin.
- Skip fabric softener. It coats fibers, which reduces absorbency and can irritate skin.
- Rinse well and dry completely. Underwear should never go on damp.
- Replace when worn. Retire a pair when the fabric thins or the elastic stops holding its shape.
Where ours comes from.
You shouldn’t have to ask where your underwear was made or what it’s made of. Here are the facts.
Read more about how we hold our supply chain accountable on our Impact page, and the research behind these choices in the Health Hub.
Fabric you can verify
Organic. Certified. Tested.
Because what touches your body should be safe by default.
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