Rayon has been around since the late 1800s, making it one of the oldest manufactured fibers in textile history. It was created to replicate the feel of silk at a fraction of the cost, and in that narrow sense, it succeeds. Soft, fluid, and with a slight sheen, it has been a staple of fashion manufacturing for over a century.
It is also one of the most chemically intensive fabrics in common use, and for anyone seeking genuinely non toxic activewear collection options, rayon's production limitations make it a poor fit. TENCEL Lyocell is a regenerated cellulose fiber in the same broad family as rayon, but the two materials are separated by nearly a century of manufacturing innovation and a fundamentally different approach to both production and fiber performance.
How rayon is made
Rayon, also sold as viscose or viscose rayon, is produced by dissolving wood pulp or other cellulose sources in a chemical solution, typically involving sodium hydroxide and carbon disulfide, and extruding it through spinnerets to create fiber. Carbon disulfide is a toxic solvent. Exposure during manufacturing is associated with neurological effects and cardiovascular risk, according to occupational health research reviewed by the US National Institute for Occupational Safety and Health.
Most rayon production is open-loop, meaning the solvents used in production are not systematically captured and reused. They are discharged as industrial waste. The environmental and occupational health implications of this process have been documented extensively in textile industry research.
The resulting fiber is soft and drapes well. What went into making it is a different story.
How TENCEL Lyocell is made
TENCEL Lyocell is produced by Lenzing AG from sustainably sourced eucalyptus wood pulp using a closed-loop solvent process. The solvent, NMMO (N-methylmorpholine N-oxide), is recovered and reused at a rate of more than 99% per production cycle, according to Lenzing's published sustainability data. The European Chemicals Agency has assessed NMMO as significantly less hazardous than the solvents used in conventional rayon manufacturing.
The closed-loop system means virtually no solvent waste enters the environment during production. Lenzing holds ISO 14001 environmental management certification and publishes detailed third-party verified sustainability reporting. The production transparency is traceable in a way that conventional rayon manufacturing is not. For a full explanation of how TENCEL is made and why the closed-loop process matters, the production story tells the full picture.
Performance: what the fiber actually does during exercise
Rayon absorbs moisture similarly to cotton. It takes moisture in and holds it at the skin surface rather than moving it away efficiently. As sweat output increases during exercise, rayon becomes heavy, stays wet, and loses structural integrity. Rayon fibers are weaker when wet than when dry, a property documented in textile science literature that accelerates degradation under the repeated wet-dry cycling of regular workout wear.
TENCEL Lyocell's fiber structure is hygroscopic in a way that draws moisture into and through the fiber, maintaining a drier skin surface under active conditions. A 2014 study in Fibers and Polymers by Kaplan et al. confirmed superior moisture management versus cotton and cotton-adjacent fibers in active wear contexts. TENCEL Lyocell fibers also maintain their tensile strength when wet, which directly affects how the fabric holds up during exercise and washing over time. For a broader understanding of what TENCEL Lyocell is, the fiber properties and production credentials are clearly documented.
Pilling and longevity
Rayon is prone to pilling under mechanical stress. The short, fine fibers that give it softness are the same reason it breaks down under abrasion. In activewear, where the inner thigh, underarm, and waistband areas experience repeated friction, rayon's surface quality degrades faster than most alternatives.
TENCEL Lyocell fibers are longer and more uniform in structure, which gives the fabric better resistance to pilling and sustained surface quality over time. A TENCEL Lyocell legging used regularly will outlast a rayon equivalent in both appearance and structural integrity.
Chemical finishes
Rayon's production process often requires additional chemical finishing treatments applied after the fiber is created. Softening agents, wrinkle-resistant treatments, and antimicrobial coatings are common in rayon garments. These finishes are not disclosed on product labels, and some, including certain formaldehyde-based wrinkle treatments, carry documented health concerns. The International Agency for Research on Cancer classifies formaldehyde as a Group 1 carcinogen in occupational exposure contexts.
TENCEL Lyocell achieves its softness, breathability, and moisture management through fiber structure rather than chemical post-treatment. The properties are inherent, not applied.
The activewear case
For a fabric that sits against your skin during elevated heart rate, open pores, and active perspiration, the production story and the in-use performance story are both relevant. Rayon falls short on both. The production process is chemically intensive and environmentally open-loop. The fiber absorbs and holds moisture, weakens when wet, and is prone to surface degradation under the mechanical demands of regular workout wear.
Bellissima's Sempre Leggings use 92% TENCEL Lyocell. Rayon was not a serious contender during material evaluation precisely because it fails the performance standard for activewear before the production concerns are even considered. A fabric that degrades during the activity it is designed for is not a performance fabric, regardless of how it feels in the store. For those evaluating other options, the rayon activewear alternatives ranked by performance and safety point consistently in one direction. Understanding where TENCEL sits relative to lyocell and modal helps clarify what the label actually means.
The straightforward answer
Rayon and TENCEL Lyocell share a broad category and a general softness profile. Everything else about them is different. The production process, the environmental impact, the performance under exercise conditions, and the durability under repeated use all point in different directions.
For activewear, TENCEL Lyocell is the answer. For understanding why the label on your clothing matters beyond fiber content percentage, rayon is the case study that makes it clearest.
Why this conversation matters more in 2026
In April 2026, the Texas Attorney General opened a civil investigation into Lululemon over the potential presence of PFAS (per- and polyfluoroalkyl substances) in activewear marketed to health-conscious consumers. The brand confirmed PFAS had been used in its durable water repellent products before being phased out in early 2024. A class action lawsuit in California made parallel allegations about misleading sustainability marketing.
The case mattered beyond Lululemon. It confirmed that synthetic fabric chemistry was being scrutinized at the state attorney general level, and that the gap between brand wellness positioning and what is actually in the fabric had become a consumer protection question. California and New York implemented broader PFAS-in-apparel bans in January 2025. Thirty state attorneys general had initiated litigation against PFAS manufacturers by the end of 2024.
What this means for anyone choosing activewear: the fiber content label is not the full picture, and brand claims are not the same as independent third-party certification on the finished textile. Understanding what the base fiber is, and how the finished garment has been verified, is the practical question this category now demands.
Sources
Texas Attorney General. (2026, April 13). Attorney General Ken Paxton Launches Investigation into Lululemon Over Potential Presence of Toxic "Forever Chemicals" in Activewear. texasattorneygeneral.gov.
U.S. Environmental Protection Agency. (2024). Our Current Understanding of the Human Health and Environmental Risks of PFAS. EPA.gov.
Kaplan, S., et al. (2014). Thermal comfort of lyocell and other fibers in active wear. Fibers and Polymers, 15(6).
Lenzing AG. (2023). TENCEL Lyocell fiber sustainability data. Lenzing Sustainability Report.
US National Institute for Occupational Safety and Health. (2020). Carbon disulfide: Occupational exposure and health effects. NIOSH Pocket Guide to Chemical Hazards.
International Agency for Research on Cancer. (2006). Formaldehyde, 2-butoxyethanol and 1-tert-butoxypropan-2-ol. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 88.
European Chemicals Agency. (2023). Substance evaluation: N-methylmorpholine N-oxide. ECHA Chemical Safety Reports.
Woodings, C. (2001). Regenerated cellulose fibres. Woodhead Publishing.