Does Period Underwear Contain Toxic Chemicals?

What are PFAS, where Kt stands, and what you can do to help.

The thing that we’re most proud of at Kt by 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.  

Last week, 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 Kt, 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 it’s of 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’ve never tested for PFAS. However, due to recent news, we pursued extra third-party testing for peace of mind. We are happy to report that Kt products are PFAS free. You can download and read the report at the bottom of this post. 

Additionally, all of the fabrics in our leakproof technology are OEKO-TEX® certified - meaning that they have been tested and cleared for any other harmful substances. 

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: 'Oh-No’ Proof Technology ™

Our Oh-No’ Proof 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 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

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