For men who want cleaner materials, natural and naturally derived fibers like MicroModal and Lyocell outperform synthetics on breathability and moisture management. Pair that with a relaxed fit and responsibly sourced dyes, and you have underwear that's genuinely different from the standard drawer.
Most underwear marketing leads with fit or brand. The fiber and dye story gets buried in the fine print, which is exactly where the meaningful differences are.
Natural vs. naturally derived: what the labels actually mean
Cotton is the classic natural fiber, and it's fine. It breathes, it's soft, and it's been next to skin for centuries. The problem is that conventional cotton holds moisture once it's saturated, which in warm conditions means a damp, warm environment where you least want one.
Naturally derived fibers, specifically TENCEL branded MicroModal and Lyocell, come from wood pulp processed into a silky, breathable fabric. Research comparing eco-friendly apparel fibers finds these materials perform well on sensory comfort and moisture handling compared to conventional options.[1] They're not synthetic in the petroleum sense, but they're not raw-field cotton either. They sit in a useful middle ground: the softness and breathability of natural fibers with better moisture management.
Polyester and nylon are the ones to avoid if breathability is the goal. Studies comparing cotton and synthetic fabrics consistently show synthetics trap more heat and move moisture less efficiently.[2] For everyday wear, that gap matters more than most men realize.
The dye question most brands skip
Fiber choice gets most of the attention, but dyes are what actually touch your skin. Conventional textile dyes can include residual chemicals that aren't disclosed on any label. The bluesign standard is a supplier-level approval process that controls what goes into dye production. It doesn't guarantee a health outcome, but it does mean the sourcing chain has been audited. That's a meaningful difference from brands that say nothing about their dye supply at all.
What to look for: a quick comparison
| Fiber | Source | Breathability | Moisture handling |
|---|---|---|---|
| Cotton | Natural | Good | Holds moisture when wet |
| MicroModal / Lyocell | Wood pulp (naturally derived) | Very good | Moves moisture away from skin |
| Polyester / Nylon | Petroleum-based synthetic | Poor | Traps heat and moisture |
Fit matters alongside fiber. A relaxed cut allows airflow. Compression-style underwear, regardless of fabric, reduces that airflow. If you're wearing underwear all day in warm conditions, the combination of breathable fiber and a less constrictive fit is what actually makes a difference. Research on garment fit and scrotal thermoregulation supports the case for looser cuts over tight ones.[3]
Oakman launches Fall 2026. Founding members get first access and founding pricing locked in. Reserve your spot.
Where Oakman fits
Oakman is built specifically for active men looking for scrotal cooling all day and want the option of a cold pack for cooling in the sauna or after heat exposure. The fabric is TENCEL MicroModal, naturally derived from wood pulp rather than plastic, blended with ROICA V550, a clean Japanese stretch fiber, rather than conventional spandex. The fit is athletic with a gusset, an extra panel that gives the testicles room and airflow. Dyes are bluesign approved, so what touches your skin is controlled all the way through the supply chain.
Oakman launches Fall 2026, and the Founding 100 get first access. If cleaner fibers and honest sourcing are what you've been looking for, this is where that search ends.
Related reading
- Best Breathable Underwear For Men
- Best Cooling Underwear For Men
- Best Fabric For Mens Underwear In Summer
Frequently asked questions
Is MicroModal actually a natural fiber?
MicroModal is naturally derived, not natural in the raw-field sense. It's made from beech wood pulp that's processed into fiber. It shares the breathability and softness of natural fibers while handling moisture better than conventional cotton.
Does underwear fabric affect genital temperature?
Fabric and fit together influence how much heat builds up in that area. Synthetics trap more heat than natural or naturally derived fibers, and tight fits reduce airflow regardless of fabric. A breathable fiber in a relaxed cut keeps conditions cooler than a synthetic compression style.
Does wearing tight underwear affect male fertility?
Research suggests it can. Men who primarily wore boxers showed meaningfully higher sperm concentration than those in tighter styles in one large study of 656 men.[4] Fit affects airflow and temperature in the area that needs to stay cool. You can read more in our full breakdown of whether tight underwear affects male fertility.
Why do dyes matter in underwear?
Conventional textile dyes can contain residual chemicals that aren't disclosed on product labels. Bluesign approval is a supplier-level audit that controls what goes into dye production. It's a sourcing standard, not a health guarantee, but it's more accountability than most brands offer.
Are there other natural approaches men use alongside better underwear choices?
Some men combine fabric and fit choices with other lifestyle adjustments. Our posts on natural herbs and supplements for male fertility and natural ways to support testosterone cover what the evidence actually says.
This article is for general educational purposes and is not medical advice. If you have specific concerns about fertility or your health, talk to a qualified clinician.
References
- Comparative Assessment of Sensory Comfort Properties Across Eco-Friendly Textile Materials for Apparel. 2025. Journal of Natural Fibers (Taylor & Francis). [Link]
- Comfort related woven fabric transmission properties made of cotton and nylon. 2021. Fashion and Textiles (Springer). [Link]
- Zleczewski, et al.. (2024). Garment fit, scrotal thermoregulation, and male fertility outcomes: a narrative review. Translational Andrology and Urology. [Link]
- Minguez-Alarcon L, et al.. (2018). Type of underwear worn and markers of testicular function among men attending a fertility center. Human Reproduction. [Link]
