The battle of the period undies: Thinx vs Knixwear

Thinx Period-Proof Underwear vs. Knixwear Leak-Proof Undies

Lately, I’ve noticed there are a number of new companies selling organic tampons and pads as an alternative to Kotex, OB, Always (feminine products that are laden with a number of chemicals; including bleach). With this topic trending, I wanted to throw in two other alternative period options - period undies and the two brands that I personally use; Thinx Period-Proof and Knix Leak-Proof Undies.

I would like to preface this with this review will be categorized as #ThingsIBoughtFromPodcastAds

Image via Knixwear Instagram page

Image via Knixwear Instagram page

I’ve been using Thinx, a US brand for the last 3 years and I will say that they have underwear for everyday of your period. They have 4 different Period-Proof underwear types with different cuts that you use depending on the heaviness of the flow. Knixwear is a Canadian brand that sells 4 styles of Leak-Proof underwear that I decided to try out while buying one of their bras (the bra didn’t work out).

One thing I want to emphasize is that using period underwear is different and than what we’re used to using tampons and pads. *gross alert* When I first started using the Thinx underwear I would described it as free flowing. We are so programmed to be afraid of leaking that the idea of letting yourself leak into your underwear on purpose is quite jarring.

The Breakdown

Underwear construction

As per the Thinx website, “Our washable, reusable undies absorb your period and are a more sustainable solution than single-use disposable products.  Every pair of THINX is made with our signature 4-layer technology for ultimate protection.

  1. Moisture-wicking cotton - A natural fiber closest to your skin for added softness and breathability.

  2. Odor-trapping lining - Neutralizes odors and fights the growth of bad bacteria.

  3. Super-absorbent fabric - Hold up to 2 regular tampons’ worth, so you never feel too *moist*.

  4. Leak-resistant barrier - So you stay fresh ‘n’ dry, even when you feel blah and crampy.”

The Knixwear website describes its undies as “Period panties look and feel like normal panties but they have a built in super-absorbent pad with leak resistant backing to prevent any period or other moisture leaks. Plus ours are seamless for max for comfort you. Suitable for heavy flows too.”

Image via Thinx website

Image via Thinx website


Thinx has underwear for everyday of your flow. As I’ve used their heaviest flow undies to their lightest flow underwear, you won’t be disappointed by the literal coverage you get with these underwear. My favourite thing about the high waisted heavy flow underwear is that, on the first day of my flow I’ll wear them to bed and I don’t have to worry about leaking through my pjs and onto the sheets. They literally got your whole butt covered!

 Three of the four Knixwear Leak-Proof undies claim to hold two tampons (the bikini, boyshort, and high rise styles) while the thong style holds 1 teaspoon of blood.  I tried the bikini style undie on my heavy day and I definitely had a leak. Whereas the thong is perfect for light days and I didn’t experience any leaks. I would advise you use both underwear for your light days and if you spot pre and post period.


Thinx has two underwear styles per flow type for their Period-Proof underwear, which means they have 6 different styles: High Waist, Hiphugger, Boyshort, Sport, Cheeky, and Thong. As I have ⅚ styles (excluding the thong), I would suggest the High Waist and Hiphugger for your heaviest days (this follows the website guid) and the Boyshort and Sport cuts for you medium days (I didn’t like the boyshort for my heavy day) and finally the Cheeky and Thong for your light days (as suggested by the website). I find all 5 of my undies to be very comfortable during my period.

Knix has 4 styles of Leak-Proof undies the bikini, thong, highrise, and boyshort. I only have the bikini and thong which I find to be really comfortable and sleek.


I would say that the Knix Leak-Proof underwear are just that, Leak-Proof but not full period underwear. Meaning, I would pair them with a Diva cup or tampon. I will say they aren’t as thick as the Thinx underwear but closer to your regular seamless underwear that you would normally buy. Which is great for your light days or pre/post period spotting. I would say that if you wanted to wear these undies under something figure-hugging you would be perfectly fine. Thinx underwear are true Period-Proof underwear and a great alternative to pads and tampons. I’ve had my Thinx underwear for 3 years and have thrown them into the washing machine after every period and I haven’t experienced any rips or unravelling. Both underwear are great quality and will cover different parts of your cycle. Further, using these underwear decreases the amount of disposable feminine products and are sustainable options.

*Cover Photo by Drew Roberts on Unsplash