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Why polyester isn’t always the wrong choice (plus, some really awesome underwear)


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Recently, I received some adorable new underwear courtesy of the lovely folks over at Dear Kate. And these undies kind of blew my mind.

What’s so interesting about Dear Kate underwear (other than the fact that they’re pretty damn cute)? Allow me to talk about monthly lady times for a moment.

You see, these are designed specifically to be worn during your period and contain a special liner to draw fluids away from your body and repel stains.

Now, I’m a lover of nice underthings. But I also have a lot of b-listers (and c-listers, honestly) hiding in the back that I wear during that time of the month. They are ugly. They are stretched out, faded, and frankly sort of pathetic. I don’t feel great when I wear them, but I always considered it a necessary precaution, especially during the first couple of days.


Having actual nice, pretty underwear that I don’t have to worry about ruining has totally changed my outlook when I get dressed. I had one less reason to feel miserable and gross. I particularly like the new Vera hipster they recently released (I have the orchid color), and want to buy a couple more.

Aside from the great concept and pretty designs, there’s one other thing that interested me about these. It’s such an innovative use of technical fabric, namely polyester.

Dear Kate was developed by Julie, whose background is in chemical engineering. She realized that so may women deal with the problems of heavy periods and overflow, and that new technology in textiles could help.

Julie did the R&D sewing herself, and is still the fit model for the brand. They’re also still manufactured in the US. I love stories like this: a woman sees a problem and how she can address it, and builds her company from there.

julie sewing throwback(1)

This is Julie sewing in the very beginning of the company.

photo (22)

This is Li Ping, one of the sewing operators who currently makes the garments in New York.

So why did Julie choose polyester to make her super absorbent gussets? Isn’t polyester just that cheap synthetic from the 70s? Isn’t it always horribly unbreathable?

For the answer to that, let’s first look at what makes a fabric breathable.

From fiber purist to poly stretch pants

Before I became a runner, I was a fiber purist. I only ever wanted to wear natural fibers and believed them to be objectively superior to anything synthetic.

In day-to-day life, I still wear natural fibers almost exclusively (perhaps with the occasional synthetic blended in, like spandex in pants, or nylon in socks). Generally, natural fibers are more breathable and feel great against the skin.

But when I began running longer distances, cotton no longer cut it. In the winter, I’d have to wear many layers of clothing when I headed out. After running for a while, my cotton leggings and t-shirts would become wet with perspiration, which is dangerous in very cold conditions. In extreme cases, it can lead to hypothermia.

In the summer, I’d sweat even more, and the moisture and salt would rub and grate against my skin, causing chafing. Let me tell you, there are few things less pleasant than being rubbed raw when you are on mile 17 on a hot day. So much pain coming at you at once.

So I began buying workout clothing in moisture wicking fabrics. I noticed that these fabrics were usually entirely synthetic, and I was confused. Aren’t synthetics supposed to be less breathable than natural fibers?

Are natural fibers really more breathable?

It’s true. In general, natural fibers are more breathable.

What does “breathable” really mean, though?

In essence, breathability refers to a fabric’s ability to maintain the equilibrium between the moisture contained in the fabric itself and the air around it. Fabrics that are constantly absorbing moisture and releasing moisture are more breathable than fabrics that don’t.


In practice, what this means is that when there is moisture released from your skin, it doesn’t become trapped in the air between your skin and the fabric.

Take linen, for example. This fiber has been used for centuries in hot climates to keep people cool in even extreme temperatures.

Wool is also very effective at maintaining that equilibrium, especially in thin layers. That’s why merino wool socks can keep your feet cool and dry, even in warm conditions (weird, huh?). Wool is a great all-weather fiber.

Cotton can also be very cool, especially when worn in very thin layers. Cotton is also quite good at absorbing moisture. You probably wear a lot of cotton in the summer for this reason.

Contrast this with a synthetic fiber like polyester. Everyday polyester doesn’t breathe in the same way, leaving heat and dampness trapped on your skin. Yuck.

Cotton will absorb about 7% of moisture, but polyester only about 0.4%. That’s a huge difference. When you buy a cheap polyester dress at Forever 21 and wear it in the heat of summer, you’ll feel that.

So why synthetics?

If all this is true, why choose synthetic fibers at all when moisture is a concern?


Put simply, not all synthetic fabrics are the same, even when they’re made out of the same fiber. Polyester fabrics are not all created equally.

Yes, natural fibers are breathable and lovely in everyday life. But where they are less successful is dealing with very high levels of moisture.

Natural fibers tend to absorb a lot of the fluid, holding onto it instead of releasing it all back into the outside air, away from the body. If you’re sweating a lot (or have a heavy period), the fabric becomes saturated. Not good in either of those situations.

This is where technology steps in, and why moisture-wicking fabrics are often referred to as a category of “technical fabrics.”

These wicking fabrics are made from blends of polyester. Remember what I said above about polyester only holding about 0.4% of moisture? In cheap polyester fabrics, this is very bad for staying dry.

But wicking polyester is woven differently. The weave is extremely permeable, meaning that moisture can pass through easily. The weave is designed so that the bits of moisture are pulled into the small holes in the weave and towards the outside of the fabric, where they can evaporate. Sometimes, additional chemical treatments assist this process (though not always).

So back to the panties.

tumblr patterns

Because they’re made with wicking fabric, moisture is pulled away from your body, and into the absorbent, thin lining within. They are extremely comfortable and, yes, breathable!

So next time you’re looking at a content tag and think about turning up your nose at polyester, consider whether it’s your everyday polyester or one of these modern fabrics. While you may still prefer natural fibers in everyday clothing (I do), when you have special concerns about moisture, technical fabrics might be the way to go.

It’s science!

PS: You can buy Dear Kate panties over here. They sent me some undies to check out, but they did not pay for this post or anything. I really love what they’re doing with these innovative fabrics!

Sarai Mitnick   —   Founder

Sarai started Colette back in 2009. She believes the primary role of a business should be to help people. She loves good books, sewing with wool, her charming cats, working in her garden, and eating salsa.

Comments 53


Super informative and helpful! I’ve been a fan of Uniqlo Airism underthings for a while, but I like the idea of these undies, with an extra lining. Thanks!


Thanks for the article. It makes me want to try those very nice panties. There would be the cost for shipping to France though… But I might let myself be tempted.


What a great post! Thank you. I love your website and I just ordered your new book on knits.

I just wanted to mention that I am one of those unfortunate people who is allergic to latex and also to spandex, so I tend to favor clothing made from natural fibers. I am still wearing 100% cotton jeans from 10 years ago because I can’t find stylish modern jeans that don’t have spandex in them. I can tolerate certain pieces of clothing with spandex (one style of Wacoal bra, for instance), but too much spandex on my body and I feel like my skin is on fire. It’s really awful and I wish clothing manufacturers would take that into account. All I am really asking for is a stylish pair of 100% cotton jeans.

Melissa S.

Janet, I know Levi’s offers some 100% cotton jeans, but pretty much you’re stuck with the “boyfriend” style. Also I don’t know if you’ve heard of Nudie Jeans but they offer a number of jeans that are really stylish and 100% cotton, and seem to be wearable by both men and women. Pricey though. But those two brands are more stylish than, say, LL Bean, which also offers jeans without spandex but they look sort of “mom jeans” to me.

The more I think about this, the more frustrated I am, actually. I’m not allergic to spandex, but the thought that practically ALL women’s jeans have to be full of spandex because all women are supposed to wear sexy skin-tight clothes, well, that thought kind of rubs me the wrong way. And unfortunately, if you’re looking for 100% denim, that kind of thing is usually made by smaller, niche companies (like Nudie), meaning you pay a lot for it.

The alternative would be learning to make your own jeans, since good denim fabric is pretty affordable, and you could adjust the fit and style to what you want. That skill might take time to learn, but it would probably be worth that time. I think I’ll add jeans-making to my own “To Learn” list.

I wish you luck finding good jeans you can wear and afford.

s j kurtz

Making jeans is addicting. Best to start with a pair that already fit , and trace them off (the Kenneth King class is very detailed for that). If you really want an education, take them apart and make a pattern/learn reverse engineering. It’s a worthwhile self-taught class about construction all by itself.


I would second Nudie jeans and heritage brands that offer women’s selvedge denim! Raw denim is a great look and the bonus is that’s it’s generally offered my small independent brands and made in the USA. You might try Raleigh Denim, Imogene & Willie and Railcar Denim. Some of their offerings do have spandex, but not all.


Thank you for the suggestions on places to try for 100% cotton jeans. I will check Nudie and the others out out. I don’t mind paying for quality jeans (especially if made in the US). I just don’t like the “mom jeans” look, LOL! I haven’t yet reached the point of trying to sew them myself, mostly because of time constraints, but it’s definitely an option.


Here’s something I often wonder when looking at “activewear” fabrics at stores: how can you tell the difference between a cheap polyester knit labelled as an activewear fabric, and a technical fabric with the same fibre make-up? It’s one of the reasons I haven’t tried making my own workout wear–I don’t want to get the wrong kind of fabric and they’re often not clearly labelled.

Hep Kara

This is exactly what I was going to say. How do you knot which is which?


I have found that a nylon/lycra blend is often best for activwear (mostly called supplex, though make sure it is the supplex with lycra before you buy, some is just plain woven nylon)! Check out Fehr Trade’s website for a big list of places to buy activewear fabric.

s j kurtz

Synthetics and workout wear is the one category where I don’t sew from scratch because sourcing good material is tricky or impossible (and I live pretty close to Seattle Fabrics, which does carry some). The good stuff trickles down slowly and forget anything high tech – it’s brand specific and unavailable to us layfolks. Unless I hijack a truck…

That said, I buy large and alter like crazy. I spend my thrift shopping time in the workout wear aisle. Pretty good stuff there (and virtually unworn!).

And a slight overshare: now that I am done with menstruation, all my undies are lovely!


I’d recommend trying out

It’s the online store for Rose City Textiles here in Portland. Most of their fabrics are overstock and mill ends from the big activewear companies (Nike and Adidas are both located here, as well as many small brands). If you search there for “wicking,” there are a lot of good options.

I find that shopping at specialty places like this is your best bet for finding the good stuff. It’s usually labeled much better than other fabric stores, even the big ones that do carry activewear fabric.


Thanks for this link! Very exciting! I have a lot of trouble finding suitable activewear fabrics. While supplex does the job, its not always optimal for every item.


Thank you for this link. In the summer I wear a lot of casual sports clothing made with UPF fabric because I have Lupus which causes me to be super photosensitive. I’ve been trying in vain to find a place where I could buy the fabric by the yard and these guys have some!!! I’m so excited now! :)


Yes, this is a problem. There are also varying qualities of activewear fabrics. “Activewear” also sometimes means swimsuit fabric–obviously not breathable. I have bought pique textured activewear fabric that still turned out to be hot. The only reliable indicator I have found this far is to look for “supplex” which is, I think, a brand name. Sometimes generics are just named something __plex. Otherwise, there are a few online retailers that specialize in activewear/outerwear fabrics.

Katie Emma

I also have an aversion to synthetics, probably because I am a handknitter and synthetic yarns are generally pretty bad, but everything you’ve said here rings true with me. I splurged on a pair of performance-fabric polyester undies to wear on runs, but now I want a drawer full to wear every day. Thanks for the info on this cool home-grown business!


What an interesting post, so very educational…. and what a great product. I think I’m going to have to try these panties. I bike to work everyday and I wear moisture wicking pants and shirts for the ride. The panties would greatly add to my comfort.


Thank you for that. I’ll certainly consider these.


Interesting. I find so many beautiful fabrics that I don’t buy because they are polyester. But….how can you tell it’s a wicking polyester????


Once I started reading sewing blogs, I started noticing this trend of aversion to synthetics, which I kinda thought was crazy! I grew up in an outdoorsy/active family, and the idea that cotton=death was kinda pounded into my head. We were never to wear cotton hiking or canoeing or skiing because once it got wet or sweaty, the chances of hypothermia (or less severely, chaffing and general discomfort as you mentioned) are greatly increased because once cotton gets wet it takes forever to dry. Synthetics and wool, only! Now, most of my casual wardrobe consists of a variety of fibers, I have always embraced synthetics and the thought of wearing cotton underwear gives me nightmares. As a geologist (and generally sweaty person), pretty much everything I wear to work needs to be fairly quick to dry. In fact, one of my main motivations to learn to sew was so that I could make cute(r) things out of synthetics to wear to work and on back-county adventures since I am out of the size range of most major outdoors labels (patagonia, etc). Thanks for the great info, I hope more seamstresses come around to the idea of un-natural fibers!


Yes, as soon as I started learning about hiking, I learned that cotton = death.


Oh, how interesting! I wouldn’t say I have an “aversion” to synthetics — they make up quite a lot of my wardrobe actually, because cheap — but almost none of my undies are synthetic b/c I was told that anything that doesn’t let that area “breathe” encourages yeast infections. It never occurred to me that the breathable tech fabrics used for workout wear could do just as well for undies!


Alas, the vast majority of synthetic garments (and yardage) don’t indicate whether they are “plain old polyester” or the newer microfibers, no doubt because most people wouldn’t know the difference.


That’s true. I find that specialty stores (like the one I linked in the comment above) are the best places to look for these fabrics.


And yay! The undies come in plus sizes! Totally getting a few pairs. Thanks!


I went to the site very excited to try these pretty undies. However, being into the plus sizes I find it very upsetting that they cost so much more for the “queen” size, which I also find insulting. Does it really take $12 more worth of material and time to make the larger sizes? I wear a 9 and find it hard to believe that it would cost that much more to make them.
I am normally not a complainer, but this all makes me very sad.


Wow that is disappointing – $48 for a pair of underpants (plus shipping and exchange rate) is… quite a lot. I’m also not impressed that it costs so much for plus size – I always figure the cost should be absorbed into the rest of the sizes (that is, XL uses less fabric so it evens out).


I’ve heard of Dear Kate before, and was very intrigued – may have to do some online shopping! :)

A question for you regarding technical poly’s – I’m not a runner, so i can understand there would be different considerations if you are, but I do hot yoga, and find that poly fabrics, even the moisture-wicking kind, start to possess an unpleasant smell even if one is vigilant about washing immediately. I don’t have that problem at ALL with cotton, so I wear cotton exclusively for my practice. I know lots of other ladies/men prefer the moisture wicking fabrics, but I do notice that funky smell a lot and I’m positive it’s the fabric – have you noticed this at all?


Hi! I’m actually in textile development and we’ve studied this problem in class. Basically, cotton is hydrophilic, meaning the fibers like water. Water can penetrate them and get through the fabric. Polyester is hydrophobic, meaning it doesn’t get along with water. It doesn’t want to let water molecules get in and around the poly molecules. What that means for stinkage is that cotton is easier to wash. When you wash it, the water and soap is getting up in there. For polys, it doesn’t let water in so it’s harder to get out smells once they get in there.

That’s the scientific-ish answer! Practically, you can try Oxy Clean soak or vinegar in the wash to get rid of the smell. I have Penguin sports wash and it doesn’t really do much for me, but my friend swears by Oxy Clean and another friend loves vinegar in the wash.


Susan is spot on! I remembered reading about this a few months ago in the column Ask a Clean Person – There are a few additional suggestions, but vinegar or OxyClean should do it.

gabriel ratchet

you might also try adding baking soda, or using a detergent that incorporates it. my sons are competitive fencers, and their gear is now all synthetic…. don’t even think about what it can smell like. i use the fragrance free arm&hammer powdered detergent and a scoop of oxyclean in hot water. gets them bright white and fit for human nasal proximity.

The Nerdy Seamstress

Thank you for this! It makes complete sense. In everyday garments, I avoid it like the plague. In work out clothes, it makes sense. Also, I wonder why some expensive clothes are made of poly, is this the same reason? They’re using higher quality poly?


It’s possible, but I somehow doubt it or they’d probably mention it as a selling point. Unfortunately, I think a lot of expensive clothes are just made from cheap stuff these days. :/


How awesome! I love the idea of these undies and especially love that you went there (about periods and that time of the month) with this post. I’m so in the same boat with the super uglies during that time and it’s nice to know that someone has thought about a solution for it!


I still prefer wool when running. It works and it’s not smelly like the syntetics are.


I like wool too! Especially in Winter, Smartwool or Icebreaker makes good stuff.


You should look into buying NZ merino – it’s what Icebreaker is made out of anyway, it’s a lightweight breathable wool knit. I believe The Fabric Store in Los Angeles (a NZ owned store) sells it, much cheaper than buying branded gear. They often have sales at the start and end of winter too – our local store is having a sale for $20/m soon (yaaaay)


I actually have some from The Fabric Store already! I haven’t had a chance to use it yet, but want to make some leggings this winter for sure!


I made three pairs of leggings from NZ merino wool knit and I can’t tell you how much I love them! Actually, I wore a pair the other day in 74 degree weather and they were wonderful!


Oh yes, yes, yes about synethetics and wicking. I have a fair amount of medical knowledge and feel like bopping doctors who tell ladies suffering with the dreaded thrush to wear cotton undies. Thrush is a fungus, it exists in the atmosphere and likes to settle wherever there is heat and moisture. It has never made sense to me to recommend cotton undies because moisture makes cotton soggy, like the cotton wool you take eye make up off with. What we really need is moisture wicking fabrics to keep us dry. Thank you Sarai for a lot of common sense. I have tried to order Dear Kate undies in the past and totally failed due to their clunky e-commerce site. I must have another go! BTW had a convo the other day at a boutique where the lovely ladies were trying to sell me a white skirt and I’m peri menopausal – no, no, no!! One day you girls may know what I mean!


I don’t recommend cotton underpants because of thrush, but because dermatitis is much less common with cotton. Also, a lot of polyester underpants are TERRIBLE and don’t breath at all, leading to more moisture (= thrush). And thrush is commensal for many of us anyway, meaning it’s living down there all the time (rather than it coming from the environment) and is more an opportunistic infection.

I bet you laughed straight in that salesperson’s face!


I do appreciate the article, but these are way out of my price range. I understand investing in a nicer garment, but there is no way I would pay $36 for one pair of panties.


Cool, another one! I just read on the A Dress A Day blog about Thinx, a company with a similar product. At the moment they have it set up that if you buy a pair of theirs, they send reusable washable cloth menstrual pads to a girl in the developing world who may be missing days of school because of the lack of supplies. Great to know that there are all of these woman-created companies developing out there thinking of these practical solutions.

Melissa S.

While we’re on the topic of underwear, have you heard of the travel underwear? The selling point is that you can wash them in the sink and they’ll be completely dry in just a few hours. So you can pack, say, two pairs of underwear for a long trip instead of lots of pairs, and you’re not trying to figure out where to stash all your dirty underwear in the middle of backpacking or something. ExOfficio is the one I’ve heard of but I’m sure there are others.


Interesting – I’d wondered how synthetics could be breathable. Not being a runner or cold-weather hiker I think I’d still avoid polyester, though, in favour of more sustainable natural fibres (certified organic cotton, wool, linen, hemp…), not only because of the unsustainable source for polyester (petroleum) but also because of toxicity concerns – antimony, formaldehyde, etc; I would guess those things are even more of a worry for fabric that’s worn against sweating skin, aren’t they? There’s the eventual disposal issue too – polyester’s a plastic. And, like others, I’ve found in the past that once synthetics get a smell in them they’ll never let it go!


I love science and clothing, so this post was right up my street!
Have you heard about copper being used in clothing? It’s good at fighting infections, especially good for women after childbirth or people post surgery.


I haven’t heard of that, I will have to look into it!


This was a really fascinating article, thanks for doing all the research! I figured there had to be a difference between the cheap poly heavy clothes and the more expensive poly-spandex wicking fabrics! Thanks too for the fabricline website, it’s hard to know what is the good stuff so I’ve only bought sport fabric if it was attached to a brand name, for example I’ve found Patagonia and Underarmor fabrics

Does anybody else suffer from the ‘bad stinkies’ after wearing any polyester/lycra/nylon product? How do you get body odor washed out of that type of fabric? I’m a total convert to wool socks, even in summer. That seems to have eliminated stinky feet for me. Workout clothes made with even the special wicking weaves still get stinky. And that stinky doesn’t seem to wash out.


For some reason mine air out fine. And I really work up a sweat when I work out. I usually end up with all my moisture wicking polyesters all sweated through. Since I work out sometimes twice a day, I just put my workout clothes in a bucket of warm water and soap, handwash and then hang to air dry on my window sill. I have everything from Nike to UA to even Forever 21 stuff and they all seem fine.

I think the trick is to air-dry.

Jean Chung

hen I was growing up in Korea, we wore these “hygiene panties” over the regular undies with pads during periods, much like Kate’s undies.

As a knitter/spinner and a designer, I definitely appreciate all natural fibers but when I dance, I prefer 100% nylon/synthetic leotards. These materials are meant to be used for certain things that natural fibers just can’t do.


These look amazing! Thanks for this post – so useful.


YES YES YES! Moisture wicking polyester is my best friend. Like you, I kept on sweating through my cotton, and for the longer runs, the heavy shirt and leggings were weighing me down. I’ve switched to moisture wicking polyester and have never looked back. At first I was a little hesitant but after doing a lot of research and remembering my fabric classes from college, moisture wicking was actually woven differently than regular ol’ polyester. Between my wicking shirts for summer and my heatgear stuff for winter, I have to say I’ve become an elitist and hate hate hate when I wake up and all my running clothes are in the hamper… It wouldn’t take long until someone figured out the same would work for those pesky monthly visits and Dear Kate has been something I have been preaching to, to every lady that comes my way.

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