Comparing Period Underwear: Knix VS Thinx

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December 4, 2017


I LOVE talking about all things period – and I’ve been pretty open about my own period routine. If you’ve been keeping up with the blog, you know that I switched to a menstrual cup over 2 years ago and have been loving it. But lately, there’s been tons of talk about period underwear. I’m a member of a variety of women’s groups and there’s always questions popping up asking if period underwear are worth it, which brand to get, etc. 

Because I want to continue minimizing my carbon footprint, be part of the conversation, and help women make a well-informed purchase – I bought a pair of period underwear from Knix and a pair from Thinx

knix underwear review, thinx underwear review

Knix Review

Cost: $39.55 (for 1 pair with tax & shipping)
Construction: Seamless, absorbant gusset
Performance: Great for medium – light days

Knix is a Toronto-based company, that sells bras, underwear and previously loungewear. I have purchased one of their bras in the past, as well as regular underwear. Their regular underwear is made from nylon and Lycra and is seamless.

Their leakproof line is designed for periods and urinary incontinence (PS. if you do leak while you run/jump/laugh, I would recommend seeing a pelvic floor physiotherapist). The bikini underwear can hold up to 2 tampons-worth of fluid, which is roughly 10mL (or 2 tsp), although they have other styles (like thongs and boy shorts).

Their leakproof underwear is designed very similarly to their regular line – both are seamless, the body is made from nylon and Lycra, the only difference is that the leakproof pair has a lined crotch (also known as a gusset), which is 86% cotton. I wore this pair on my medium – light days (the tail-end of my cycle). And I liked them because they were thin and seamless (aka. not as thick as Thinx) and I didn’t need any of the additional lining.

Taking care of them was also easy – I washed them in cold water and threw them into the dryer (although they do recommend that they should be hung to dry).

2 MONTH UPDATE: Still going strong! Like I’ve said, I’ve purchased other Knix underwear in the past and it still looks good as new. 

6 MONTH UPDATE: The ironed seam (at the gusset) has come loose, which is incredibly disappointing (I have not noticed this issue with my older Knix underwear). This has left some of the padding exposed. That said, I will continue to use them until them though (especially since they were over $40!). 

2019 UPDATE: I bought another leakproof pair for $9 (!!!) at Knix’s first warehouse sale. I also bought a few bras (evolution, 8 in 1), pyjamas (I hope they consider selling these again), and evolution top which I have yet to wear. I really like this company, and I’m so happy that I found a wire-free bra that feels and looks great! 

2020 UPDATE: The PJs have been re-released!

NEW PURCHASE: I also purchased the leakproof Dream Short for $45 (Canadian). The gusset is a bit bigger compared to the regular underwear and does extend more at the front and back – though not completely all the way.

This last picture shows the extended pad that is ‘high absorbency.’ I haven’t worn them yet, but I imagine paired with a cup they might be a great combo for overnighters.

Thinx Review

Cost: $43.97 (for 1 pair with discount and shipping)
Construction: Not seamless, fully lined, extra layer from front of the gusset extending to the back
Performance: Great for heavy days and overnight

Thinx is an American-based company that only sells period-proof underwear – although they do have a sister company called Speax designed for women who experience urinary incontinence. Thinx is moisture-wicking, anti-microbial, absorbent and leakproof. My pair is made with breathable PUL fabric, and the inside layer is 95% cotton (which is great for those who suffer from chronic vaginal infections). I purchased the scarlet hiphuggers, that are designed to hold 2 tampons worth of fluid. Like Knix, they have various styles (like boy shorts) that hold different amounts of liquid. 

These are fully lined and feel heavier than Knix. I wore these during my heavier days, including overnight. They felt very snug and secure, adding to that extra sense of overnight security. When I did notice some slight leakage during the day and night, the Thinx absorbed everything and did not stain any clothes or sheets! Taking care of the Thinx was also rather simple. After I finished using them, I rinsed them in water, machine washed in cold water and tossed them in the dryer. They do advise to hang them to dry, but I’ve stopped doing that. 

2 MONTH UPDATE: The threads of the band have started to get a bit loose and pull at the top. For a product that costs more than $50, this is really disappointing. I don’t believe that all pairs have this band, so it may not affect the other pairs. However you may want to make this consideration if purchasing the hiphuggers. 

6 MONTH UPDATE: No other threads have come loose. Aside from that minor issue 4 months ago, everything has remained the same. 

2019 UPDATE: I have 2 pairs of the Thinx now, the last pair I got on sale for about $32.00 Canadian. If you can get them on sale, I would recommend it for heavier days.  

2020 UPDATE: A recent report has come out indicating a discovery of chemicals in the gusset of the underwear: “polyfluoroalkyl substances (PFAS) on the inside layers of the crotch. These are chemicals known to be toxic to humans, even at very low levels, and have been linked to cancer and fertility problems.” The original report is linked here – where the author sent in a pair of unwashed Thinx and Lunapads to be tested for chemicals.

Since then, Thinx has published a blog post about their products being body safe and have stated: “The truth is that US regulations aren’t as strict as those in the EU, which is why we comply with both US regulations and the EU’s REACH regulations. For example, while the US has banned 11 chemicals from cosmetics, REACH bans 1,328. By complying with REACH, we’re also supporting REACH pre-market testing requirements — all to protect our customers’ safety and wellbeing.”

knix underwear review, thinx underwear review

Final Thoughts

Overall, this has been a pricey experiment – but I know that I will save on the cost of pads and liners, water usage (for any accidents), and decrease waste! It’s been great having a dedicated pair of underwear to wear during my period.

I am interested in seeing if any Canadian companies like Knix will make a similar style of product and what the price point may be, and if they would offer them in bundles to make them more accessible. 

If you want to save $15 on a pair of Knix, use this link!

If you want to save $10 on a pair of Thinx, use this link!

Check out my article where I discuss other reusable menstrual products! Please note, I haven’t tried all offerings of period underwear. I wrote this post a few years ago when Knix and Thinx were leaders in the market (and still are), and since then have amassed quite an array of products. I hope to try some other brands in the near future. However, if you’ve tried alternate brands and want to share your experience – I’d love to hear about it in the comments!

Lastly, if you love learning about periods and want to keep in the flow, sign up for my monthly newsletter called The Flow for great and informative content like this! And you’ll also get a FREE hormone balancing meal plan while you’re at it!

27 Responses

  1. Laura says:

    Thanks! I wanted to try these and bought my first pair of Knix yesterday (chose them because they are Canadian), but I was second-guessing myself and your review helped.

  2. Tania says:

    Just wondering whether you had to pay Canadian duties when the package arrived from Thinx? Considering ordering them but they’re so expensive!

    • No! Thankfully I didn’t have to pay any duties 🙂

      They are quite expensive, and I hesitated for a while I was lucky enough to snag my second pair when the hiphuggers went on sale.

      If you are okay with waiting, you can always see if they have a Black Friday/Cyber Monday sale!

  3. Ariette says:

    Overall, do you like your thinx or knix better? <3


    • Hi Ariette! I really like them both, but if I had to choose one, I would get the Thinx because I prefer the lining for my heavier days and overnights. It makes me feel more secure. I do wear them with a cup though, and not on their own. Hope that helps!

      • Natasha says:

        I also prefer Thinx as the absorbant gusset is longer. The Knix gusset isn’t as long, and isn’t any longer than a short panty liner, si if you don’t bleed perfectly down into a small area, go Thinx for sure.

  4. Sarah says:

    I let knix know that I had a problem with their leakproof and the proceeded to say they are for “backup” only and their underwear is not meant to replace tampons/cups etc. That is certainly not how they are being advertised/marketed. Just a heads up!

    • Thanks Sarah! Yes, after I bought my first pair and opened it, it was clear that I would have to use a cup with them. I tend to stick with that particular pair as my flow tapers off.

  5. Emilie says:

    I don’t know if you ever found out about other companies, but I know Mme L’Ovary is Montreal area based. And I have not tried them, but I believe Viita is also Canadian. I’d be interested if you have any others!

  6. Nyla says:

    Re: 2019 Update:

    Does the liner still extend all the way to the back? I can’t tell by their marketing on the site, but it looks like the gusset is still in the usual spaces.

  7. Tess says:

    Thinx lined all the way to the back waist band? I agree there is extra material there but it’s doesn’t have the PUL going all the way to the back waist band. Or at least mine doesn’t. I poured water on mine and squeeze the material. The gusset showed no water leakage but the back did.

    • You’re right, I looked at my red pair more closely and the thicker material found at the gusset doesn’t extend all the day to the back. But for me I do find that it is enough coverage (when used with a menstrual cup), and it’s more lining than a regular pair of underwear would have. Thank you for your feedback!

  8. Tess says:

    I like the looks of the Knix but afraid the lining isn’t far enough forward in the front.

  9. Lily says:

    Any information on chemicals in Knix? I wonder how much of their technology is similar to Thinx.

  10. Rosi says:

    Great article. Thank you for the tip about Knix Warehouse Sale. It looks like they have a virtual warehouse sale beginning… TODAY!

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