We make bamboo boxer shorts, not cotton. So take the comparisons here with that in mind. We have tried to be straight about where cotton wins, because for a lot of people it does. Competitor specifications checked against their own sites in August 2026.
Why cotton is still the default
Ask a GP or a dermatologist what to wear and most will say cotton. There are good reasons for that, and they are worth stating before any brand tries to sell you something else.
It breathes. Cotton is a natural fibre with a loose weave that lets air move.
It is cheap. A multipack costs a few pounds, which matters when underwear is a consumable.
It is forgiving. Hot wash, tumble dry, bleach a stain out. Cotton survives things that would ruin most alternatives.
It is well understood. Nobody needs to explain what cotton is or make claims about it.
Where to actually buy cotton knickers in the UK
Four routes, depending on what you care about. We do not sell cotton, so none of these is a plug.
| Where | Fabric | Sizes | Returns | Best for |
|---|---|---|---|---|
| M&S | Cotton and cotton-rich, wide range | Broad | Standard high street policy | Multipacks, availability, price |
| Y.O.U Underwear | 95% GOTS certified organic cotton, 5% elastane. Pre-washed and shrink-resistant | UK 6 to 22 | 30 days, unworn and unwashed only | Organic cotton, ethical sourcing |
| Organic Basics | Organic cotton, from around £13 | Standard range | Ships from Denmark | Organic, minimal styling |
| Supermarkets and fast fashion | Cotton-rich blends | Broad | Standard | Cheapest per pair |
Y.O.U is the one to look at if organic matters to you. GOTS certification is meaningful, the fabric is pre-washed so it does not shrink on you, and they donate a pair to Smalls For All for every pair bought. Two things to know: sizing stops at UK 22, and returns are unworn and unwashed only, which on underwear means you are committing before you know if it fits.
M&S is the honest mass-market answer. Wide range, easy to buy, cheap in multipacks, and you can try before you commit if you are near a store.
What to look for when buying cotton underwear
Check the actual percentage. "Cotton" on a label can mean a 60% cotton blend. If you want the properties above, look for 95% or higher, or a stated 100% cotton body with an elastane waistband.
Check where the cotton is. Many pairs sold as cotton have a synthetic body and a cotton gusset only. That is not the same thing, though for intimate health a cotton gusset is the part most guidance actually refers to.
Look at the waistband. This is where cheap pairs fail first. A wide, flat band lasts longer and digs less than a narrow band of elastic in a folded-over channel.
Check the seams. Overlocked seams sit proud and can rub. Flat or bonded seams sit smoother.
Check whether it is pre-washed. Cotton shrinks. Pre-washed or pre-shrunk fabric means the pair you get is the size you keep.
Look for OEKO-TEX Standard 100 or GOTS. Cotton is a natural fibre but the dyes and finishes are not, and finishing agents cause more contact reactions than the fibre does. Both certifications mean the finished fabric has been tested.
Where cotton does less well
It absorbs moisture and holds it. This is the main one. Cotton takes up sweat readily and then stays damp, which is why it feels clammy after exercise or on a humid day.
It takes a long time to dry.
It creases and loses shape. Cotton has little natural stretch, so most pairs blend in elastane, and that is usually what wears out first.
It offers no thigh coverage in most cuts. If your problem is thighs rubbing, the fibre is not the issue. The leg length is, and most cotton knickers do not have one.
Cotton, bamboo viscose and modal
| Cotton | Bamboo viscose | Modal | |
|---|---|---|---|
| What it is | Natural fibre, spun | Regenerated cellulose from bamboo pulp | Regenerated cellulose from beechwood |
| Feel | Softens over time | Soft from the first wear | Soft from the first wear |
| Moisture | Absorbs and holds | Moves it, dries faster | Similar to bamboo |
| Wash | Very forgiving | Cool wash, no softener, air dry | Similar to bamboo |
| Price | Lowest | Mid to high | Mid |
| Best for | Everyday, cool weather, low maintenance | Warm days, long days, people who dislike damp fabric | Similar to bamboo |
All three are cellulose. The difference is that cotton is spun from the fibre as it grows, while bamboo viscose and modal are dissolved and reformed. That processing is why they feel different and why they need more care.
What "chemical-free" means, which is nothing
You will see bamboo underwear sold as chemical-free. It is not, and neither is cotton.
Bamboo viscose is made by dissolving bamboo pulp in a solvent and reforming it into fibre. Ours uses a closed-loop process where the solvent is recovered and reused rather than discharged, and it does not use carbon disulfide. That is a meaningful difference from conventional viscose. It is not the absence of chemistry.
Conventional cotton is grown with pesticides and finished with dyes and softening agents. Organic cotton reduces the growing side, which is what GOTS certification covers. Neither is chemical-free.
What is actually checkable is OEKO-TEX Standard 100 or GOTS. Look for those rather than for the word natural.
If your skin reacts to underwear
Textile contact dermatitis is real, and it is more often caused by dyes, finishing agents and elastic than by the fibre itself.
Practical things that help: choose undyed or lightly dyed fabric, wash new underwear before wearing it, use a non-biological detergent and skip fabric softener, look for OEKO-TEX Standard 100 or GOTS, and avoid raised or overlocked seams in areas that already react.
We are not going to tell you bamboo viscose is hypoallergenic or antibacterial. Neither claim is substantiated for viscose made from bamboo, ours included, and plenty of brands in this category say otherwise.
If your skin is reacting persistently, see a GP or a pharmacist. Contact dermatitis, eczema and fungal conditions look similar and need different treatment, and no fabric is a substitute for finding out which one you have.
Where we fit
We make bamboo viscose boxer shorts with a 6 or 9 inch leg, UK 8 to 30, dyed to OEKO-TEX Standard 100. They exist to stop thigh chafing, which no fibre choice fixes on its own.
If you want the cheapest, most forgiving option, buy cotton. If you want organic and certified, buy Y.O.U or Organic Basics. If you find cotton clammy on warm days, or you want a longer leg, that is where we come in.
Our returns are 60 days and we replace your whole first order if the size is wrong, which is worth comparing against the unworn-and-unwashed policies elsewhere.
These are very comfortable and cool to wear. Prevents chafing when wearing dresses. They have been a godsend in this hot weather. They wash well too!
Marlene, UK, verified review
Questions
What is the best 100% cotton underwear for women?
For certified organic, Y.O.U Underwear use 95% GOTS certified organic cotton with 5% elastane in UK sizes 6 to 22. For range and price, M&S. Note that almost nothing is literally 100% cotton, because a pair with no elastane will not hold its shape.
Is 100% cotton underwear good for women?
It is breathable, cheap and easy to wash, which is why it is the usual default. Its weakness is that it absorbs moisture and holds it, so it feels damp after you sweat. For everyday wear in cool weather it is a sensible choice.
What underwear do gynaecologists recommend?
General guidance tends toward breathable fabric, a cotton gusset, and a fit that is not tight. Style matters less than those three. This is general information rather than medical advice, and if you have a persistent problem it is worth speaking to a GP or pharmacist rather than changing underwear and hoping.
Where can I find 100% cotton women's underwear?
M&S, John Lewis and most supermarkets stock cotton and cotton-rich ranges. For certified organic cotton, Y.O.U Underwear and Organic Basics both specialise in it.
What does 100% cotton actually mean on underwear?
Usually that the body is 100% cotton. Almost all pairs have some elastane in the waistband or leg, otherwise they would not hold shape. Check the composition rather than the front of the pack.
Is bamboo underwear better than cotton?
Not universally. Bamboo viscose is softer from the first wear and handles moisture better. Cotton is cheaper, more forgiving in the wash and lasts longer under rough treatment. We go through it properly in our two-year switch.
Is bamboo viscose natural?
It is made from a natural raw material and chemically processed into fibre, which is why it is called regenerated cellulose rather than a natural fibre. So is modal, and so is Tencel.
Does cotton stop chafing?
No, and neither does any other fibre on its own. What stops thigh chafing is leg length, and most cotton knickers do not have one. We cover it on our anti-chafing shorts page.
