Your skin is your largest organ. It is also a permeable barrier, not an impermeable wall. While it does a remarkable job of protecting your body from the external environment, research in dermatology and toxicology has made clear that certain substances, particularly lipophilic or fat-soluble compounds, can cross the skin barrier and enter the bloodstream over time. What you wear against your skin every day is worth the same scrutiny as what you apply to it.
This is not a fringe concern. It is one that dermatologists, environmental scientists, and textile researchers have been investigating for decades, and the picture that emerges is worth understanding before you next reach for a fast fashion staple or a synthetic activewear set.
The Skin as a Barrier and an Absorber
The outermost layer of the skin, the stratum corneum, acts as the primary barrier between the body and the environment. It is highly effective at blocking pathogens, large molecules, and most water-soluble substances. However, smaller molecules, particularly those that are fat-soluble or lipophilic, can penetrate this layer through a process called transdermal absorption.
Transdermal absorption is well established in medicine. It is the principle behind nicotine patches, hormone patches, and certain pain relief gels. The same mechanism that allows therapeutic compounds to be delivered through the skin also allows unwanted chemical compounds to enter the body through prolonged skin contact with textiles.
The rate of transdermal absorption depends on several factors: the size and solubility of the molecule, the duration and area of skin contact, skin temperature and hydration, and whether the skin barrier is intact or compromised. Clothing worn close to the body across large surface areas for extended periods creates conditions that favour absorption of any compounds present in the fabric.
The practical implication is straightforward. A single brief contact with a textile chemical is unlikely to be significant. But wearing a garment against your skin for eight to sixteen hours a day, multiple days a week, over months or years, is a different exposure profile entirely. Cumulative low-level exposure is what researchers focus on, and it is what warrants attention when choosing what to wear.
Synthetic Dyes and What They Leave Behind
The global textile industry is one of the largest users of synthetic chemical dyes in the world. Most fast fashion garments are dyed using azo dyes, a broad class of synthetic colorants that account for roughly 60 to 70 percent of all textile dyes used commercially. Azo dyes are popular because they are inexpensive, produce vivid colours, and bond readily to synthetic fibres.
The concern with certain azo dyes is that under specific conditions, including heat, sweat, and friction, they can break down and release aromatic amines. Some aromatic amines are classified as potentially carcinogenic under the European Union's REACH chemical regulation framework. This is why the EU has banned the use of specific azo dyes in textiles that come into contact with skin, a regulation that many countries outside Europe do not enforce.
Garments manufactured outside EU regulatory frameworks, particularly in markets with limited chemical oversight, may contain azo dyes that would not pass EU REACH testing. This is most relevant to fast fashion and low-cost synthetic garments. The risk is not from a single wearing but from regular prolonged skin contact with fabrics that have not been tested or certified for skin safety.
Beyond azo dyes, textile processing involves a range of additional chemicals including fixatives, optical brighteners, softeners, anti-crease treatments, and flame retardants. Some of these compounds are designed to remain in the fabric after washing, which is precisely what makes them useful in manufacturing and precisely what makes their skin contact profile worth considering.
Microplastics: The Problem You Cannot See
Synthetic fibres including polyester, nylon, acrylic, and spandex are essentially plastics in fibre form. They are derived from petrochemicals and share the molecular characteristics of plastic polymers. When these fabrics are worn, washed, or even simply moved against the skin, they shed microscopic fibres known as microplastics or microfibres.
A single wash cycle of a polyester garment can release hundreds of thousands of microfibres into wastewater. Research published in environmental science journals has found synthetic microfibres in marine ecosystems, drinking water, food sources, and human tissue samples including the lungs, blood, and placenta.
In Water and Ecosystems
Synthetic microfibres pass through wastewater treatment systems and accumulate in waterways and oceans. They have been found in the tissue of marine organisms across the food chain, including fish consumed by humans.
In the Body
Microplastics have been detected in human blood, lung tissue, and placental tissue in peer-reviewed research. The long-term health implications of this accumulation are still being studied, but their presence in human tissue is now well-documented.
What Fibres Shed
Synthetic fabrics shed microfibres during wear, not only during washing. Direct skin contact with synthetics means the skin surface is in regular contact with microplastic particles, particularly in areas of friction and movement.
A Different Profile
Natural fibres also shed, but they release biodegradable particles rather than persistent plastic polymers. Wool, cotton, and silk fibres break down in the environment and do not accumulate in ecosystems or tissue in the same way.
Other Chemical Treatments Worth Knowing About
Dyes and microplastics are the most widely discussed concerns, but textile chemistry extends well beyond colouration. Many garments undergo chemical finishing treatments to achieve the properties printed on their labels.
- Wrinkle-resistant and easy-care finishes often involve formaldehyde-based resins, which can cause contact dermatitis in sensitive individuals and are classified as a known human carcinogen by the International Agency for Research on Cancer
- Antimicrobial treatments, used widely in activewear and socks, frequently use silver nanoparticles or triclosan compounds, both of which raise environmental and skin sensitivity concerns with prolonged exposure
- Water-repellent finishes on outdoor and performance fabrics have historically relied on per- and polyfluoroalkyl substances, commonly known as PFAS or forever chemicals, which persist indefinitely in the environment and have been detected in human blood worldwide
- Optical brighteners used to make whites appear whiter are activated by UV light and can cause photodermatitis in some individuals
- Flame retardants applied to certain synthetic fabrics, particularly children's sleepwear and furniture textiles, include organophosphate and halogenated compounds associated with endocrine disruption
A garment does not have to look or smell like it contains chemicals to contain them. Most textile treatments are colourless, odourless, and invisible, which is exactly why certification matters.
Natural Fibres Versus Synthetic: The Skin Contact Comparison
The distinction between natural and synthetic fibres is not simply about sustainability or texture. At the level of daily skin contact, the two fibre categories present meaningfully different exposure profiles.
Natural fibres are not automatically chemical-free. Cotton grown with heavy pesticide use and dyed with unregulated synthetic dyes can present similar concerns to a synthetic garment. The relevant question is not simply natural versus synthetic, but whether the fibre has been grown, processed, and dyed under a certified and audited framework that limits harmful chemical use across the entire supply chain.
What to Look for When Choosing What to Wear
The practical takeaway is not that you need to throw out your wardrobe. It is that the claims on a swing tag are worth interrogating, and that certifications from independent auditing bodies are more meaningful than brand-authored sustainability statements.
- EU REACH compliance means a product has been assessed against the European Union's comprehensive chemical regulation framework, which restricts or bans hundreds of substances of very high concern
- OEKO-TEX Standard 100 certification tests finished garments for harmful substances including pesticides, heavy metals, formaldehyde, and certain azo dyes
- ZQ certification for merino wool covers not only animal welfare and land management but also the processing standards applied to fibre from farm to finished yarn
- Toitu Envirocare certification in New Zealand independently audits environmental management systems including chemical use, wastewater treatment, and sustainability practices in manufacturing
- Choosing natural fibre garments with verifiable chain of custody reduces exposure to synthetic microplastics entirely and limits chemical treatment risk when combined with reputable certification
The most sustainable garment is one you can wear for a decade.
Choosing fewer, better pieces made from certified natural fibres is not only a skin decision. It is a meaningful reduction in your exposure to the full cycle of synthetic textile chemistry, from the dye bath to the microfibre your washing machine releases into the water table every cycle. What you wear is a daily decision. It is worth making it consciously.
In the second part of this series, we look specifically at how NZ Charly and our yarn partner Woolyarns approach dye safety, chemical certification, and responsible manufacturing, and what that means for the person wearing the finished garment.