The thing that we’re most proud of at Knix is that people trust us with their bodies. They trust us to photograph them, they trust us to share their stories, and above all— they trust us to make intimates that are safe, non-toxic and chemical free.

Recently, a necessary spotlight was cast towards exactly what goes into making period underwear. What makes them leakproof? What materials are used? Are these fabrics safe? In short: What exactly am I putting near my vagina?   

What are PFAS?

PFAS (polyfluoroalkyl substances) are a large family of synthetic chemicals that are commonly used as a stain or water repellent. The two most common are PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). You might have heard about them in the news lately, as recent studies have revealed them to have negative effects on your health and the environment. They’re harmful because they can’t be broken down — which could be especially dangerous if they’re added to underwear, coming in direct contact with an extra sensitive area of your body. 

At Knix, we put a lot of care into crafting great products and a lot of thought towards creating underwear that’s both safe and effective. We’ve been intentional about avoiding stain repellents and fabric treatments (these same repellents are often used on carpets or industrial machines— yikes!). For starters, our Leakproof Underwear materials and technology are manufactured in Italy. Not only are they manufactured here because of the higher quality, but also because the European Union has a substance restriction on toxic PFAS chemicals.  

What's in our Underwear?

Because of these laws, we had initially never tested for PFAS. However, due to news in early 2020, we pursued extra third-party testing for peace of mind. As an industry standard, these tests only spot 20-30 main chemicals (like PFOA), which our Leakproof Underwear were cleared for. You can save and read the report at the bottom of this post. 

June 3, 2021 Update: 

There are 9000 different kinds of PFAS, but there aren’t tests available for all of them yet. However as a community member gratefully pointed out to us, all PFAS contain Fluorine (this is the F in PFAS). What does this mean? If our underwear was free from Fluorine, we’d be free of all PFAS. 

Because of this feedback, we sought out extra testing to confirm that there is no Fluorine in our Leakproof Underwear. 

After our initial tests, we began ongoing testing for Fluorine in January 2020, and we are happy to report that our Leakproof Underwear are Fluorine free. Testing for Fluorine is now part of our testing process going forward. You can check out what a negative Fluorine report looks like at the bottom of this post in a sample 2022 report for leakproof, super leakproof and cotton super leakproof. (2022 test results added May 6, 2022)

Additionally, all of the fabrics in our leakproof technology are OEKO-TEX® certified. You can find the fabric breakdown of all of our products on each of their product pages. Here’s what makes up the liner of our Leakproof underwear: 

 Gusset Liner: 86% cotton, 10% spandex, 4% carbon

We opted for cotton because it’s a natural, breathable fibre next to your skin. Our carbon cotton fabric has inherent bacteriostatic and anti-odor properties. Carbon has been used in air and water filtration for years, and is natural and safe. 

 Gusset: Fresh Fix Technology® 

Our Fresh Fix Technology is a polyester layer that absorbs and traps moisture which is paired with a polyester based water impermeable membrane, making our products both absorbent and leakproof. 

What’s Next?

Having launched in 2013, we pride ourselves on being pioneers within the period underwear and leakproof underwear industry and as such we are leading by example— by calling for more transparency and stricter regulations in this growing category. 

Whether you are looking at our products or those from another brand, we want you to 1) know what’s going into those products and 2) ensure that you have access to information that backs up claims such as “anti-odor”, “absorbent” and “leakproof”. Sign our change.org petition to get on board and show your support.

Thank you for trusting us to make your intimates. If you have any other questions about product safety, please don’t hesitate to reach out to our team at info@knix.com. 

Fluorine Results from November 2020:

PFAS Results from January 2020: