Certified activewear:
why it really matters for your health
We all pay attention to what we eat. But do we really pay attention to what we wear? When we work out? When we sweat?
1. Your skin is a sponge, not a barrier
We tend to think our skin protects us from the outside world, and it does, mostly. But it also absorbs. That's actually one of its jobs: moisturisers, pain-relief gels… they all work precisely because skin lets certain molecules through.
Skin is our largest organ. During exercise, your body temperature rises, blood vessels dilate and pores open to regulate temperature. This natural process, sweating, also makes your skin more permeable. What you're wearing against your skin at that moment matters.
During exercise, your pores open and absorb whatever is on their surface.
Tight leggings, sports shorts, a Lycra jumpsuit: these pieces stay in direct, prolonged contact with the most sensitive and absorbent areas of the body. The crotch, the chest, the armpits.
2. PFAS: what you're not told about your activewear
PFAS (per- and polyfluoroalkyl substances), nicknamed 'forever chemicals', are a family of more than 10,000 synthetic compounds. They're found in everyday products: non-stick pans, food packaging, raincoats, and on a large scale in activewear too.
What are they used for in textiles?
In the activewear industry, PFAS are used for several commercial reasons:
- Water-repellent finishes (DWR): so water and sweat bead on the fabric
- Stain-resistant treatments: to avoid marks and keep that 'new' look longer
- Anti-odour agents: some antibacterial treatments contain fluorinated compounds
- Surface softeners: for that 'peach skin' feel so typical of big sportswear brands.
What the science says
According to the European Chemicals Agency (ECHA) and several epidemiological studies, long-term exposure to PFAS is linked to hormone disruption, thyroid disorders, a higher risk of certain cancers, fertility problems and a weakened immune system. These substances don't break down in the environment or in the human body.
The crotch area problem
This is the detail that blew up on social media: the crotch of a pair of leggings is one of the areas with the most chemical treatments (to resist friction and sweat). Yet the skin there is among the most absorbent on the body: thin, full of blood vessels and often damp during exercise.
Wearing PFAS-treated leggings several hours a week, year after year, is no longer a theoretical question. It's a cumulative, silent exposure that's completely overlooked.
3. Why exercise increases exposure
An oversized shirt in treated synthetic fibres is a minor risk compared with sports leggings, for simple reasons:
- Heat: physical effort raises your body temperature, which makes your skin more permeable
- Moisture: sweat creates the ideal conditions for chemicals to migrate to the skin
- Duration: a yoga class, a run, a fitness session often means 1 to 2 hours of continuous direct contact
- Compression: a close-fitting garment doesn't just sit on your skin, it presses against it the whole time
- Frequency: we don't wear our workout clothes once a year. For many of us, it's 4 to 7 times a week
Put together, these factors make activewear one of the most intimate things you wear (in every sense). Far more exposing than jeans or a dress.
4. What is certified activewear?
Certified colourful activewear isn't just a marketing line. It means every component (fabric, thread, printing inks) has been tested by an independent lab and confirmed free from harmful substances. Not a promise. A licence number you can check.
There are several levels of certification. Here are the most important ones to know:
| Certification | What it guarantees | Level |
|---|---|---|
| OEKO-TEX Standard 100 | Free from more than 1,000 harmful substances (PFAS, heavy metals, endocrine disruptors, allergens) in the finished fabric | Essential |
| OEKO-TEX ECO PASSPORT | Certification for the inks and chemicals used in dyeing and printing, guaranteeing that the ink itself is safe | Essential for prints |
| Bluesign | Checks the whole production chain, from fibre to finished fabric, with factory audits | Gold standard |
| Global Recycled Standard (GRS) | Traceability of recycled materials. It doesn't certify the absence of toxic substances but guarantees the recycled content is genuine | Traceability |
| Made Green in Italy | A certification from the Italian Ministry of the Environment, combining environmental criteria with the absence of toxic compounds | Premium |
| No certification | No guarantee about the chemical make-up of the fabric or surface treatments | Unknown risk |
What to remember
A fabric made from recycled material (Econyl, recycled polyester…) doesn't guarantee it's free from PFAS. What counts is the certification of the finished fabric and of the inks used to print it. Without certification you can check with a licence number, a 'healthy clothing' claim is just greenwashing.
UJO goes for double certification: fabric + printing
Most shoppers don't know that even a certified fabric can be 'contaminated' by uncertified printing. Standard sublimation inks or solvent-based inks can contain heavy metals (lead, cadmium), phthalates and other harmful compounds that sit right on the surface of the garment, in direct contact with your skin.
So truly safe activewear needs to have:
- A fabric certified OEKO-TEX Standard 100 (or Bluesign)
- Printing inks certified OEKO-TEX ECO PASSPORT: water-based inks, with no solvents, no gases and no heavy metals
- A traceable production chain.
5. Certification comes at a price
We're often asked why UJO leggings cost more than high-street leggings or those from big international sportswear brands. The answer fits in one sentence: certification comes at a price.
Producing clean textiles takes longer processes, lab testing and factories that play by the rules. Every certification has to be renewed each year, audited by independent bodies and paid for by the factory. Those costs are passed on in the price of the fabric.
In an industry where speed and margins often set the rules, cheap chemical treatments are a common shortcut. Choosing certification means accepting higher production costs to protect your health.
It's exactly like food. Organic produce costs more because avoiding pesticides takes more demanding processes. It's the same logic for activewear; it's just that nobody has explained it clearly yet.
Choosing your clothes for your health
6. How to choose activewear that's safe for your health
Wherever you buy your activewear, here are the questions to ask and the answers to expect:
- Look for the OEKO-TEX Standard 100 logo on the product page or the label.
- Ask where the fabric comes from: eco-friendly activewear made from recycled or organic certified fibres (OEKO-TEX, GOTS…) is a good sign, but check that the finished fabric is certified too.
- If it's printed, check the printing: if the garment has a print, are the inks certified? Water-based, solvent-free? Ask the brand directly.
- Be wary of vague claims: 'natural', 'eco-friendly' or 'sustainable' without a matching certification can be greenwashing.
A good habit to get into
Before buying new activewear, ask the brand one simple question: 'Are your fabrics OEKO-TEX Standard 100 certified?' The quality of the answer (and how quickly it comes) will tell you a lot.
That's exactly what we do at UJO STUDIO. Our certifications are available on our website, on every product page.
Frequently asked questions
Are PFAS really dangerous in activewear?
Yes. According to several studies, PFAS are persistent substances linked to hormone disruption, thyroid disorders and a higher risk of certain cancers. During exercise, your pores open and your skin absorbs more, which increases exposure. The crotch area, which has lots of blood vessels and is often targeted by waterproofing treatments, is the most at risk.
What is OEKO-TEX Standard 100 certification for activewear?
It's an international certification guaranteeing that a fabric has been tested for more than 1,000 harmful substances, including PFAS, heavy metals and endocrine disruptors. It's issued by independent labs and renewed every year. It's the minimum standard to ask for in any garment worn directly against the skin.
Is eco-friendly activewear always PFAS-free?
No, not necessarily. A fabric can be made from recycled materials (Econyl, recycled polyester) and still have been chemically treated during dyeing or finishing. Only OEKO-TEX Standard 100 certification on the finished fabric guarantees it's free from PFAS and other harmful substances.
How can I tell if activewear is safe for my health?
Look for OEKO-TEX Standard 100 (fabric), OEKO-TEX ECO PASSPORT (printing inks), GRS (traceability of recycled materials) and GOTS labels. These certifications are checked by independent bodies and come with a licence number you can verify on the OEKO-TEX website.
Are all the big sportswear brands affected by PFAS?
Contrary to what many people think, plenty of big international brands have been called out for using PFAS in their sportswear ranges, especially in water-repellent and anti-odour finishes and in dyeing! Things are changing under pressure from EU regulation, but without certification you can verify, there's no way to know for sure what a garment really contains.
Move without compromising your health
Every UJO piece is made with fabrics certified OEKO-TEX Standard 100 at the very least. Fabric and printing inks. No chemical shortcuts, no greenwashing, just proof.