Naturally derived fibers like TENCEL MicroModal and Lyocell outperform both synthetics and heavy cotton for keeping you cool and dry. They pull moisture away from skin, breathe well, and don't trap heat the way polyester does.
By 10 a.m. you already know if you made the wrong call. Fabric, not brand, not price, is what decides whether you stay comfortable through a commute, a workout, or a full day in the heat, and the differences between materials are real enough to measure.
How the main fabric categories compare
Cotton, synthetics, and naturally derived fibers each behave differently against skin. Here's what the evidence and basic textile science show:
| Fabric | Breathability | Moisture wicking | Heat retention | Softness |
|---|---|---|---|---|
| Standard cotton | Moderate | Absorbs, holds moisture | Moderate to high when wet | Good |
| Polyester / nylon | Low | Wicks fast, dries fast | High, traps heat | Variable |
| TENCEL MicroModal | High | Wicks and releases moisture | Low | Very high |
| TENCEL Lyocell | High | Wicks and releases moisture | Low | High |
Cotton's problem isn't that it's bad. It's that it holds onto moisture. Once it's damp, it stays damp and warm. Synthetics like polyester wick fast but don't breathe, so they move sweat off skin and then trap heat against it. Peer-reviewed comparisons of eco-friendly apparel fibers show naturally derived materials like Lyocell and MicroModal manage both moisture and sensory comfort better than conventional alternatives. [1]
Fit compounds the fabric effect. Tight underwear in any material presses against the body and restricts airflow where you need it most. Research consistently links tighter garment fit to elevated genital temperature, and elevated genital temperature is associated with lower sperm quality in men. [2] [3] A looser cut in a breathable fiber is a different category of product from a compression-fit synthetic, even if both claim to be performance underwear.
- Cotton: Fine for cool days, poor choice when you're active or it's hot.
- Polyester and nylon: Fast-drying but heat-trapping. Better for short athletic bursts than all-day wear.
- MicroModal and Lyocell: Derived from wood pulp, naturally breathable, softer than cotton, and cooler against skin throughout the day.
One sourcing note worth knowing: synthetic fabrics have come under scrutiny for chemical residues. Studies have detected microplastics in human tissue samples, and separate research links certain synthetic-adjacent chemicals to hormonal disruption. [4] [5] Naturally derived fibers don't carry the same concerns, though dye and finishing processes still matter, which is why sourcing transparency is worth asking about.
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. Launching Fall 2026. The Founding 100 get first access.
Related reading
Related reading
- Best Fabric For Mens Underwear In Summer
- Best Breathable Underwear For Men
- Best Cooling Underwear For Men
Frequently asked questions
What is the coolest fabric for men's underwear in hot weather?
Naturally derived fibers like MicroModal and Lyocell consistently outperform cotton and synthetics for staying cool. They wick moisture away from skin and release it into the air rather than holding it, which keeps the fabric from warming up against your body.
Is cotton or polyester better for men's underwear?
Cotton breathes better than polyester but holds moisture once it's wet, which makes it warm and uncomfortable. Polyester dries faster but traps heat. Neither performs as well as naturally derived fibers for all-day comfort in warm conditions.
Does underwear fabric affect genital temperature?
Fabric and fit together influence how much heat builds up in that area. Synthetic fabrics that trap heat and tight fits that restrict airflow both contribute to elevated genital temperature. Breathable, looser-fitting underwear helps that area stay cooler throughout the day.
Does underwear affect fertility?
Research shows that elevated scrotal temperature is associated with lower sperm quality, and garment fit is one factor that influences scrotal temperature. Men who wore boxers showed meaningfully higher sperm concentration than those in tighter styles in one large study. Fabric choice matters because it affects how much heat builds up.
What is TENCEL MicroModal and why is it used in underwear?
TENCEL MicroModal is a branded fiber derived from beechwood pulp. It's softer than cotton, more breathable than most synthetics, and manages moisture well, releasing it rather than holding it. Those properties make it a practical choice for underwear designed to keep you cool and dry.
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]
- 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]
- Hu CJ, Garcia MA, Nihart A, et al. (Yu XZ senior author). (2024). Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis. Toxicological Sciences. [Link]
- Rodprasert W, Toppari J, Virtanen HE. (2021). Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men. Frontiers in Endocrinology. [Link]
