Some period underwear has been found to contain PFAS, the class of fluorinated chemicals used to make fabrics resist liquid — which is why several brands now publish PFAS testing or explicit PFAS-free statements. Whether a given pair contains PFAS depends on the brand and the gusset construction, and there is no labelling requirement, so the only reliable check is the brand's own published statement or a third-party lab result. Tampon Tribe's Ashers period underwear are made without PFAS, using organic cotton and modal in four moisture-wicking layers rather than a treated synthetic.
What are PFAS?
PFAS stands for per- and polyfluoroalkyl substances — a large family of synthetic chemicals built around carbon-fluorine bonds. That bond is one of the strongest in organic chemistry, which is exactly why the chemicals are useful and exactly why they are a problem. They repel water and oil extremely well, and they do not break down easily in the environment or in the body. That persistence is why they are often called forever chemicals.
They turn up in non-stick cookware, waterproof outerwear, stain-resistant carpet, food packaging and firefighting foam. Textiles are one of the most common consumer applications, because a fluorochemical finish is a cheap and effective way to make fabric shed liquid.
Why would PFAS end up in period underwear?
Because period underwear has to do something ordinary underwear does not: hold liquid without letting it through. There are two broad ways to achieve that.
The first is construction — layering absorbent fabric so the liquid is drawn in and held, with a barrier layer underneath. The second is chemistry — treating the fabric so liquid beads and runs off rather than soaking through. A fluorochemical finish is the most common version of that second approach.
A brand using the second route gets thinner fabric and faster wicking. It also gets a garment whose performance depends on a chemical finish sitting against skin.
Do all period underwear contain PFAS?
No. This is worth stating plainly, because coverage of the issue often implies otherwise. PFAS in period underwear is a real finding in specific tested products, not a property of the category. Plenty of period underwear is made without it.
What is true is that you cannot tell by looking, and you cannot tell from the price. A garment with a fluorochemical finish looks and feels much like one without.
How can you tell whether a pair contains PFAS?
There is no labelling requirement for PFAS in textiles in most of the United States, so the packaging will not tell you. In practice there are three things to look at, in descending order of usefulness.
A third-party lab result. The strongest evidence a brand can offer is a test report from an independent laboratory, with a date and a batch, published where you can read it. Some brands do this. Most do not.
An explicit written statement. A brand saying in writing that its product is made without PFAS is meaningful — it is a claim they can be held to. Vaguer language is not the same thing. "Non-toxic," "clean" and "natural" have no legal definition in this category and no bearing on PFAS specifically.
The gusset material. This is the one most buying guides skip. If a brand publishes its composition and the absorbent layers are natural fibres rather than treated synthetics, the question largely answers itself. If the composition is not published at all, that absence is itself information.
What do certifications actually cover?
Certifications are useful but narrower than people assume, and each one answers a different question.
Oeko-Tex Standard 100 tests the finished textile for a list of harmful substances. Current versions of the standard include limits on certain PFAS, but it is a test of the finished fabric against a defined list, not a blanket guarantee about every chemical that could exist.
GOTS is a supply-chain certification: it verifies organic fibre content along with environmental and social criteria across processing and manufacturing. It is not primarily a finished-product chemical test, which is why a product can hold one certification and not the other.
Neither is a substitute for a brand telling you what its product is made of.
What should you ask a brand?
Four questions get you most of the way:
- What is the gusset made of, layer by layer?
- Is the product made without PFAS — stated in writing?
- Has it been tested by a third-party lab, and can I see the report?
- Which certifications does it hold, and what does each one cover?
A brand that can answer all four quickly is a brand that knows its own supply chain. A brand that answers with adjectives is telling you something too.
Where Tampon Tribe stands
Ashers period underwear are made from soft organic cotton and modal with four moisture-wicking absorbent layers, and are made without PFAS, chlorine, titanium dioxide, added fragrance or dyes. The fabric is certified to Oeko-Tex Standard 100. Absorbency comes from how the layers are built rather than from a chemical finish.
The complete material list for every Tampon Tribe product, along with published third-party test results, is on What's Actually In It. More detail on the underwear itself is on the organic cotton period underwear page, and you can browse the six Ashers styles in sizes XXS to 4XL.
Frequently asked questions
Do Tampon Tribe period underwear contain PFAS?
No. Ashers period underwear are made without PFAS. The absorbent layers use moisture-wicking organic cotton and modal rather than a fluorochemical-treated synthetic.
Are PFAS banned in period underwear?
There is no general federal ban on PFAS in textiles in the United States, and no labelling requirement, though several states have passed or proposed restrictions. Because rules vary and change, a brand's own published statement or a third-party lab result remains the most reliable check.
Does Oeko-Tex certification mean a fabric is PFAS-free?
Not by itself. Oeko-Tex Standard 100 tests a finished textile against a defined list of harmful substances, and current versions include limits on certain PFAS. It is a test against that list rather than a guarantee covering every possible chemical.
Can you wash PFAS out of period underwear?
No. A fluorochemical finish is applied to bond with the fabric and is designed to survive laundering, which is what makes it durable in use. Washing is not a way to remove it.