Shein is the world's largest online-only fashion retailer. It adds thousands of new products daily, ships to 150+ countries, and sells dresses for the price of a coffee. We looked at what those clothes are actually made of.
The answer is not reassuring.
Overview
Shein is the most synthetic-heavy major fashion brand in the world. Not close to the industry average — far beyond it. The fast fashion industry averages ~69% synthetic. Shein exceeds that by over ten percentage points.
What Shein Is Made Of
Based on the Changing Markets Foundation's research and our own product-level label analysis of 50+ Shein products:
Polyester is overwhelmingly dominant. Cotton appears primarily in basic t-shirts and jeans. Natural fibres like linen, wool, and silk are virtually absent.
Category Breakdown
Dresses: 95-100% Polyester
Shein's dress category is a polyester monoculture. Across 50+ labels we examined, nearly every dress was 95-100% polyester. The occasional "satin" or "silk" dress? Check the label — it's polyester with a shiny finish. Even items styled to look like cotton or linen are synthetic underneath.
Tops & Blouses: 90-100% Polyester
Blouses are almost universally polyester. T-shirts offer slightly more cotton, but the default is still synthetic. Crop tops, bodysuits, and going-out tops — polyester throughout.
Jeans & Trousers: 70-80% Cotton
This is Shein's only reasonably natural category. Denim requires cotton for structure, so even the cheapest jeans contain majority natural fibre. However, the polyester content (15-25%) is higher than you'd find at denim-focused brands, and elastane adds another 2-5% synthetic.
Activewear & Loungewear: 85-95% Synthetic
Zero natural fibres. 85-95% polyester or nylon, 5-15% elastane. These are the garments you sweat in most — against bare skin — then wash, shedding maximum microplastics.
Knitwear: Mostly Acrylic
Sweaters and cardigans that look like wool are typically acrylic — the cheapest synthetic substitute. Acrylic is the least breathable common fabric and the highest microplastic shedder.
The Chemical Problem
Beyond fabric composition, independent testing has raised serious concerns about chemicals in Shein products:
- CBC Marketplace (2021): Found a Shein jacket with lead levels 20 times over Health Canada's limit for children's jewellery.
- South Korean government (2022): Found toxic chemicals up to 3,300 times over EU safety limits in Shein children's products, including phthalates (endocrine disruptors).
- Discrepancies: Researchers have found differences between what Shein claims on product pages (e.g., "recycled polyester") and what actual garment labels state.
- evoluSHEIN programme: Only 8.3% of SHEIN-branded products met their own evoluSHEIN material standard in 2024.
Shein has disputed some of these findings but has not provided independent verification to counter them.
How Shein Compares
| Brand | Synthetic % | Primary Material |
|---|---|---|
| Shein | 64-82% | Polyester |
| Zara | ~27% | Cotton/Polyester |
| H&M | ~22% | Cotton |
| Gap | ~5-10% | Cotton |
| Reformation | 2.56% | Natural fibres |
Shein uses 3x more polyester than Zara and nearly 4x more than H&M. The price point reflects the material cost: when a dress costs $5, the fabric came from a petrochemical plant.
Why It's So Cheap
The economics are straightforward:
- Polyester costs roughly half as much as cotton to produce
- Shein's business model depends on extreme volume at ultra-low prices
- Cutting fabric cost is the primary lever — and polyester is the cheapest option
- Manufacturing in volume with standardised synthetic fabric allows thousands of new SKUs daily
You're not getting a deal. You're buying the cheapest possible material at a small markup.
The Verdict
Shein is the most synthetic-heavy major fashion brand we've examined. At 64-82% synthetic material, it far exceeds the industry average. Dresses, tops, and blouses are near-universally polyester. The only categories with meaningful natural fibre are jeans and basic t-shirts.
The chemical safety concerns — with independent tests finding toxic substances thousands of times over safety limits — add another dimension of risk beyond fabric composition alone.
If you shop at Shein and want to avoid synthetics, stick to cotton basics and denim. Everything else is almost certainly plastic.
Methodology
This audit draws on the Changing Markets Foundation's "Synthetics Anonymous" research, Shein's own sustainability disclosures, independent chemical testing by CBC Marketplace and the South Korean government, and Fibr's product-level composition analysis of 50+ Shein items across multiple categories. Material mix percentages are sourced from the Changing Markets Foundation audit. Category breakdowns are based on Fibr's direct label analysis.