"Healthiest" has a testable meaning in textiles, and it is not the fibre name on the label — it is what chemistry remains in the finished fabric. A conventional cotton finished with formaldehyde resins is not healthier than a certified polyester. The two questions worth asking are: does the fibre let skin breathe, and is the finished fabric certified free of harmful substances?
How do breathability and moisture behaviour differ?
| Fibre | Breathability | Moisture absorption | Skin-contact suitability |
|---|---|---|---|
| Combed cotton | Very high | High (up to 25% of weight) | Excellent |
| Organic cotton (GOTS) | Very high | High | Excellent |
| Modal / lyocell | High | Higher than cotton | Excellent |
| Bamboo viscose | High | High | Good — chemically processed |
| Polyester | Low | Very low (0.4%) | Good if certified, poor for prolonged wear |
Which health claims are actually verifiable?
OEKO-TEX Standard 100 tests the finished fabric for around 1,000 harmful substances — azo dyes, formaldehyde, heavy metals, pesticide residues. Class I is the strictest tier, written for articles in contact with baby skin, and it is the level to specify for anything worn against the body all day. GOTS goes further for organic goods, covering the whole processing chain rather than only the end product.
What does “organic” actually tell you?
Organic certification concerns how the cotton was grown, which matters environmentally. It does not by itself guarantee the dyeing and finishing were clean — that is what GOTS processing criteria and OEKO-TEX testing cover. For skin health specifically, the finishing certificate is the one that counts.
When are synthetics the healthier answer?
Not always cotton: for high-sweat activity, a certified polyester or polyamide that moves moisture away from the skin prevents the chilling and chafing that a soaked cotton T-shirt causes. Health here means the right fibre for the use, not the natural one by default.
What does a practical specification look like?
For babywear and underwear: GOTS organic combed cotton, OEKO-TEX Class I, undyed or reactive-dyed, no formaldehyde easy-care finish. Our dyeing runs through our partner dyehouse under GOTS and OEKO-TEX Class I certification, and we hold BCI for conventional cotton. We do not hold GRS, and we do not claim it.
Altunkaya Tekstil supplies GOTS organic and BCI cotton knits, OEKO-TEX Standard 100 Class I certified — min. 50 kg per colour. WhatsApp: +90 536 304 67 29