Committed to never using leather, feathers, fur or skins since 2001, we are continually investing in research and development for animal leather alternatives. In 2022, Stella McCartney launched the world’s first-ever luxury bag crafted from Mylo™ – a verified vegan alternative to animal leather made using mycelium, the root-like structures of fungi. This pioneering material innovation is grown in a lab by our long-term partner, Bolt Threads.

About Bolt Threads and Mylo™

Unlike many leather alternatives, Mylo™ is crafted with renewable mycelium from fungi, furthering our mission to move away from fossil-based synthetics. The entire material production process is maintained within the United States and the European Union, to retain full transparency and minimise our geographic footprint.

How is Mylo™ made?

Following more than 5,000 iterations, Bolt Threads transformed mycelium into Mylo™️ – a biobased, OEKO-TEX® STANDARD 100 Certified alternative to animal leather that is soft, supple and has significantly lower environmental impacts than raising livestock. Cows require extensive resources and years to raise, while the mycelium used to craft Mylo™ is grown in less than two weeks inside a vertical farm facility, powered by 100% renewable energy (Mylo Unleather).

Fungal cells are mixed with sawdust and organic material. Dense mycelial networks rise from the substrate, forming soft foam-like mats in weeks versus the years it takes to raise livestock. Once mature, the mycelium is harvested and the remaining substrate is composted.

Mylo™ is created with 85% mycelium from fungi and 15% lyocell (regenerated cellulose fibres), then finished with a water-based polyurethane (PU) that enhances its durability. As part of our joint commitment to green chemistry and minimising social and environmental impacts, Mylo™ is coloured at a LWG gold-rated tannery with bluesign®-certified dyes  – ensuring consumer and environmental safety and assurance.

The process of tanning stabilises the collagen or protein fibres in skins so they actually stop biodegrading – otherwise, the leather would rot right in your closet.


While Mylo™ is not yet biodegradable at its end of life, we are always monitoring and measuring our processes to reduce impact. Finished animal leather is not biodegradable – it is heavily treated with toxic chemicals and cannot biodegrade.


Together, with Bolt Threads, we are on a journey to continually improve the composition of Mylo™ – reducing and removing the use of synthetics and plastics – and maintaining transparency in our supply chain.

  • Mycelium is the naturally abundant and infinitely renewable, root-like system of fungi.
  • It sits beneath the mushrooms that sprout up across forest floors and in gardens.
  • Mycelium is a complex and connected network of lattices, weaving across the natural world and holding together Mother Earth’s surface.

Why Mylo™ is the future of fashion

In 2017, Stella McCartney partnered with the visionary scientists and innovators at Bolt Threads. Bolt Threads grow mycelium in a vertical farming facility with just air, water and mulch to recreate a process that naturally occurs beneath the forest floor, using ingredients found in nature.

Mylo™ feels more substantial and elevated in comparison to many other animal leather alternatives, thanks to the way it is created. The mycelium is harvested as a ‘foamy layer’ – uniquely mimicking the microstructure of collagen – giving the final material a supple warmth and sponginess that is not possible in 100% synthetic options.

Additionally, Mylo™ is treated by highly skilled artisans who add a special finish that protects and enhances the luxurious feel of the material. This is created according to Green Chemistry principles – without the use of harmful chemicals like dmfA and chromium, which are commonly used in animal leather production.

Why we believe in replacing animal leather

As well as being needlessly cruel, the environmental and social impact of producing animal leather is incredibly high. Animal agriculture accounts for around 19% of the world’s total greenhouse gas emissions and is driving the destruction of our rainforests.(1)

According to the WWF, the farming of cattle for beef and leather products is responsible for 80% of the Amazon’s deforestation. Around 1.4 billion hides and skins of animals were used in global leather production in 2020 alone. That is approximately one animal for every five people on the planet. (2)

Leather tanning is commonly outsourced to developing countries, where people must work in poor conditions with little safety or protections in place and are exposed to harmful and carcinogenic tanning chemicals. In Bangladesh, 90% of tannery workers die before the age of 50. (3)

Discover more about our cruelty-free alternatives to animal leather.

As a woman-led brand, we have always stood out. We are proud to be eco-weirdos, and hope you will join us in our mission to end the needless deaths of animals for fashion.

x Stella

Which of the United Nations’ Sustainable Development Goals does Mylo™ support?

  • 8. Decent Work and Economic Growth
  • 9. Industry, Innovation and Infrastructure
  • 12. Responsible Consumption and Production

1 Agricultural subsidies and global greenhouse gas emissions ( 22703-1

2 ‘What are the biggest drivers of tropical deforestation?’, WWF. (

3 Bangladesh's toxic tanneries turning a profit at an intolerable human price | Employment | The Guardian