When you sweat, your skin absorbs more than just air. Research cited by reviewers at The Filtery and Bottlecup points to studies showing that synthetic activewear can leach chemicals like BPA, phthalates, and PFAS directly through the skin during exercise. The brands below stand out in editorial coverage from The Good Trade, The Filtery, Lezat, and Bottlecup for using certified organic, natural, or plant-derived fabrics that sidestep those concerns without sacrificing comfort or function.

1. MATE the Label MOVE by MATE Organic Cotton Activewear

MATE the Label's MOVE collection includes sports bras, biker shorts, and leggings made from 92% organic cotton and 8% elastane, all manufactured in Los Angeles. The brand uses non-toxic dyes and maintains a restricted substances list to keep carcinogens and endocrine disruptors out of production. Reviewers at The Good Trade tested the Organic Stretch Scoop Bra and Biker Shorts during morning runs and found the bra "thick and really supportive without feeling hot or constricting," with both pieces holding shape and color through multiple washes. The Filtery's reviewer noted wearing MATE leggings for over two years and described them as genuinely comfortable for moderate workouts, walking, and everyday wear.

Why it stands out: MATE is a certified Climate Neutral brand and a member of 1% for the Planet. The entire MOVE collection is ethically made in the US, and the brand's commitment to non-toxic dyes and organic sourcing is verified through its manufacturing practices.

Things to know: The Filtery's reviewer noted a small hole developed in the crotch seam after about 18 months of regular wear, and recommends sizing up for a fully protective fit. The lighter colorways in biker shorts can be slightly sheer due to fewer layers of cotton fabric. These pieces are better suited to moderate intensity workouts than high-impact cardio.

2. Reprise TENCEL Leggings and Sports Bras

Reprise builds its leggings, bike shorts, and sports bras from 86% TENCEL Lyocell and 14% ROICA EF385, a recycled elastane sourced from pre-consumer materials. TENCEL is a plant-based fiber made from sustainably sourced wood pulp in a closed-loop manufacturing process that recycles water and solvents, making it significantly cleaner than conventional synthetics. All dyes are certified non-toxic and organic by both OEKO-TEX and GOTS, and every piece is made ethically in the United States.

Why it stands out: Reprise is noted by The Filtery as the most inclusive brand in the natural fiber activewear space across sizes. The TENCEL fabric delivers a soft, buttery feel that performs more like a synthetic than a raw natural fiber, making it a practical bridge for people transitioning away from conventional spandex-heavy leggings. The adjustable drawstring waistband is a feature that sets these apart from most competitors.

Things to know: The elastane content at 14% is higher than some other brands on this list, which may matter to those seeking the lowest possible synthetic content. TENCEL is technically a semi-synthetic rayon, not a raw natural fiber, so it is best understood as a cleaner alternative rather than a fully natural option.

3. Pangaia Plant-Based Activewear Collection

Pangaia makes activewear using a bio-based nylon derived from castor bean oil rather than petroleum, offering leggings, shorts, sports bras, tanks, and long-sleeved tops for both men and women. The brand is a certified B Corp with documented climate and supply chain goals. In addition to its stretchy activewear line, Pangaia offers a wide range of 100% organic cotton sweatshirts, track pants, and tees that double well as workout wear.

Why it stands out: The Filtery's reviewer specifically reaches for Pangaia leggings and compression shorts during intense workouts, describing them as comfortable, flattering, and supportive during high-intensity cardio. The brand's B Corp certification and transparent sustainability commitments are consistently highlighted in editorial coverage as markers of accountability.

Things to know: Pangaia's stretchy activewear uses bioplastic, meaning the nylon is plant-sourced but still technically a plastic polymer. Some research suggests bioplastics retain certain toxic attributes. The Filtery's reviewer acknowledges this tradeoff directly and recommends treating the bio-based pieces as a performance option while reserving organic cotton pieces for lower-impact days.

4. Wellicious Organic Cotton Yoga and Activewear

Wellicious is a brand founded in London whose activewear is made from GOTS-certified organic cotton sourced from Peru, combined with compostable elastane that breaks down without releasing harmful substances into the environment. The brand holds Cradle to Cradle certification for material health, confirming the absence of harmful toxins, additives, and microplastics. Wellicious also operates a take-back program for garments that are no longer worn.

Why it stands out: Bottlecup highlights Wellicious as one of the few brands achieving Cradle to Cradle material health certification, a rigorous standard that goes beyond basic organic labeling. The compostable elastane is a meaningful differentiator: most activewear with stretch relies on petroleum-based spandex, but Wellicious uses an elastane verified by Hohenstein to biodegrade without toxic residue.

Things to know: Wellicious ships internationally and is available to US consumers, though pricing reflects the premium European manufacturing and certification standards. The brand's focus is primarily yoga and moderate intensity movement rather than high-impact sport. US shoppers should confirm current shipping options and pricing in USD before ordering.

5. Zone by Lydia Hemp and Organic Cotton Activewear

Zone by Lydia, founded by Olympic gold medalist Lydia Lassila, makes activewear from a blend of hemp and organic cotton with only 5% elastane in pieces that require stretch. Hemp is naturally antibacterial, odor-resistant, breathable, hypoallergenic, and temperature-regulating, making it suited to movement-heavy workouts. All dyes are OEKO-TEX 100 certified and use low-impact processes, and the brand delivers in plastic-free, compostable packaging.

Why it stands out: Bottlecup notes that Lassila personally vets suppliers to ensure fair labor practices, adding a layer of ethical accountability beyond fabric certifications. The hemp-forward fabric blend is one of the more unusual and genuinely plastic-free options in the activewear market, and the low elastane percentage keeps synthetic content minimal.

Things to know: Zone by Lydia is an Australian brand. US consumers can order online, but should verify current US shipping availability and expect pricing in USD to reflect international shipping costs. Hemp fabric can feel slightly more textured than cotton or TENCEL, which may require an adjustment period for those accustomed to very smooth synthetic leggings.

6. Organic Basics Activewear

Organic Basics offers a range of activewear and loungewear built from GOTS-certified organic cotton, with select pieces incorporating TENCEL and recycled materials. The brand is recognized by The Good Trade as a strong pick specifically for the loungewear and activewear category, praised for combining accessible price points with genuine organic certification. Their activewear line includes leggings, sports bras, and shorts designed for everyday movement and moderate intensity workouts.

Why it stands out: Organic Basics is one of the more affordable entry points into certified organic activewear, making it accessible for people who want to transition away from conventional synthetic workout clothes without a significant price jump. GOTS certification covers both the organic fiber content and the social and environmental standards of the entire production process.

Things to know: Organic Basics is a Danish brand with strong US availability through its website. Some pieces in the line use recycled materials alongside organic cotton, so shoppers who want purely natural fibers should check individual product pages carefully. The activewear range is more limited in scope than brands focused exclusively on performance sport.

How to Choose the Right Natural Fiber Activewear

• Prioritize third-party certifications: GOTS (Global Organic Textile Standard) is the most comprehensive certification for organic activewear, covering both fiber content and production conditions. OEKO-TEX Standard 100 confirms the finished garment is free from harmful substances. Look for at least one of these on any piece you buy.
• Match the fabric to your workout intensity: Organic cotton and hemp are ideal for yoga, Pilates, walking, and low-impact movement. TENCEL Lyocell handles sweat better and suits moderate cardio. For high-intensity sessions, a bio-based or TENCEL blend with a small percentage of elastane offers better performance without relying entirely on petroleum-based synthetics.
• Check the elastane percentage: Almost all stretchy activewear contains some elastane or spandex. Brands using bio-based elastane (derived from corn or other plant sources) or recycled elastane from pre-consumer waste are meaningfully cleaner than those using conventional petroleum-based spandex. A small percentage (5 to 14%) is generally considered acceptable in otherwise natural-fiber garments.
• Avoid recycled polyester marketed as sustainable: Bottlecup and The Filtery both flag that recycled synthetic fibers can shed microplastics and may release chemicals more readily than virgin synthetics when exposed to sweat. Recycled polyester is not the same as natural or organic fiber, and should not be treated as a clean activewear option.
• Consider your budget and use case: Certified organic activewear typically costs more than conventional options. If budget is a constraint, prioritize organic certification for the pieces with the most skin contact during sweaty workouts, such as leggings and sports bras, and be more flexible on outer layers or activities with minimal sweat.

The single most important step is checking for a legitimate third-party certification like GOTS or OEKO-TEX before buying. Marketing language like "natural" or "clean" is unregulated, but a certification label means an independent organization has verified the claim. Start there, and the rest of the decision becomes much easier.