If your undies are rubbing, riding up, or turning swampy by midday, the culprit is usually the fabric. The wrong fibre traps sweat, ramps up odour, overheats you in the Aussie heat, and can even make chafing a daily ritual. Get the material right and everything changes: cooler, drier, softer, and properly supported—whether you’re training, travelling, or sitting at a desk.
This 2025 guide compares seven leading underwear fabrics head-to-head—bamboo viscose, MicroModal, merino wool, cotton, polyester microfibre, nylon/elastane blends, and silk—so you can pick with confidence. For each one, you’ll get plain-English explanations, real pros and cons, how they breathe and handle moisture, pouch-compatibility and support, care and durability, plus sustainability and health notes. After reading, you’ll know what’s best for chafe-free everyday wear, sweat-heavy workouts, long-haul flights, or special occasions—and why. On to the fabrics.
1. Bamboo viscose (SLY Collective): ultra-soft, breathable and pouch-friendly
Bamboo viscose hits that sweet spot between everyday comfort and technical performance. In SLY Collective’s pouch boxer briefs, it teams with a longer leg and an ergonomic inner pouch to keep you cool, supported, and chafe-free from commute to couch.
What it is
Bamboo viscose is a regenerated cellulose fibre made by dissolving bamboo pulp and extruding it into ultra-fine filaments. In underwear it’s typically a soft jersey knit blended with elastane for stretch, giving a silky hand-feel and close fit.
Key benefits
You’ll notice the comfort first, then the all-day freshness. Bamboo viscose is widely praised for breathability and moisture handling, with a naturally smooth feel that’s kind to skin.
- Ultra-soft hand-feel: Feels luxe against the skin from day one.
- Breathable and moisture-wicking: Helps move sweat off the skin to reduce clamminess.
- Cool-touch comfort: Regulates heat better than basic cotton when things warm up.
- Low-odour wear: Often reported to resist odour build-up between washes.
- Great for sensitive skin: Fine, smooth fibres reduce friction points.
If you want to explore our range, why don’t you take 20% off your first order – use SLY20 at the checkout. Remember you have a ‘first pair guarantee’ as well, so you’ve got nothing to lose.
Potential drawbacks
No fabric is perfect, and bamboo viscose is no exception. Treat it right and it lasts; treat it hot and it can fade fast.
- Heat sensitive: High dryer heat can weaken fibres and shrink garments.
- Can be less durable than synthetics: Softer knits may pill over time.
- Dries slower than performance polyester: Not ideal for back-to-back sweaty sessions.
- Eco-claims vary by maker: Viscose processing can be chemical-intensive unless well managed.
- Slightly pricier than basic cotton: You’re paying for comfort and feel.
Breathability and moisture control
Bamboo viscose breathes well and wicks reliably for everyday wear, outperforming basic cotton once you start to sweat. It doesn’t dry as quickly as polyester microfibre, but it maintains a cooler, drier microclimate than cotton when the temperature climbs.
Pouch-compatibility and support
This fabric shines in pouch designs. SLY’s built-in pouch separates to stop skin-on-skin contact, cutting chafe and sticking, while the ergonomic shape lifts and supports for all-day ease. The longer leg helps prevent ride-up and thigh rub during walks, flights, and long shifts.
If you want to explore our range, why don’t you take 20% off your first order – use SLY20 at the checkout. Remember you have a ‘first pair guarantee’ as well, so you’ve got nothing to lose.
Care and durability
Cold gentle wash, line dry or low heat only. Turn inside-out, use a wash bag, and avoid harsh heat to minimise pilling and preserve elasticity. Follow this routine and bamboo viscose keeps its softness and shape far longer.
Sustainability and health notes
Bamboo grows quickly and needs fewer inputs, but viscose production varies—look for responsible, low-impact processing and safety certifications. By staying cooler and drier, bamboo viscose helps maintain a comfortable environment for the testes—something urologists generally encourage for comfort and support, especially with pouch styles.
Best for
If you want everyday softness without the swamp, bamboo viscose is a winning base layer—especially when paired with a smart pouch and longer leg.
- All-day, warm-climate wear
- Chafe-prone thighs and sensitive skin
- Desk-to-errands comfort with light activity
- Travel and long-haul flights
- Guys who want a softer, eco-leaning option without going full synthetic
2. MicroModal (modal): luxurious softness with excellent moisture control
If you want a fabric that feels premium yet works hard in the heat, MicroModal is a standout. It’s buttery-soft, breathes better than cotton, and handles sweat with ease—making a strong case as the best material for men’s underwear in hot Aussie conditions.
What it is
Modal is a regenerated cellulose fibre derived from beechwood. MicroModal uses even finer filaments for extra softness and drape. In underwear, it’s typically a lightweight knit with a touch of elastane for stretch and recovery.
Key benefits
MicroModal’s comfort is obvious the moment you pull it on, and the performance holds up through long, warm days.
- Exceptional softness: Silkier than cotton and many bamboo blends.
- Excellent breathability: Lets heat escape to keep you feeling fresher.
- Efficient moisture wicking: Draws sweat off skin and helps it evaporate quickly.
- Shape retention: Quality MicroModal resists shrinking and pilling over time.
- Light and smooth: Low bulk under trousers, no scratchy seams.
- Colourfast: Holds dye well for longer-lasting blacks and brights.
Potential drawbacks
MicroModal’s fluid drape can mean less built-in structure—support is about the cut.
- Premium price: Costs more than basics.
- Needs smart patterning for support: Best paired with a supportive pouch and elastane.
- Heat care required: High dryer temps can stress fibres.
Breathability and moisture control
Compared with cotton, MicroModal stays cooler and drier once you start sweating. It allows airflow and actively moves moisture away from the skin, making it a reliable choice for warm weather and sweaty commutes.
Pouch-compatibility and support
The silky knit sits perfectly in ergonomic pouch designs, which lift and separate to stop sticking and chafe. Add a decent elastane content and you get consistent, body-following support that lasts all day—something many urologists value for comfort.
Care and durability
Wash cold on a gentle cycle, use a wash bag, and line dry or low tumble. Treated well, quality MicroModal resists pilling, keeps its shape, and stays luxuriously smooth.
Sustainability and health notes
When sourced from reputable producers (e.g., Lenzing MicroModal), it’s made in a closed-loop process that recovers over 99% of solvents, using wood from responsibly managed forests, and is biodegradable. Generic modal varies, so check brand transparency. The cooler, drier microclimate can help reduce friction and irritation.
Best for
If you run warm, sweat easily, or just want everyday luxury that performs, MicroModal is hard to beat.
- Hot-weather, all-day wear
- Heavy sweaters and commute-to-gym routines
- Sensitive skin and anti-chafe comfort
- Travel and long sits
- Premium comfort seekers who still want performance
3. Merino wool: temperature-regulating and odour-resistant
Merino is the natural performance fabric that earns its keep when the weather swings or the day runs long. It regulates temperature, shrugs off odour, and stays comfortable even when you’re working up a sweat—making it a serious contender for the best material for men’s underwear beyond basic cotton.
What it is
Merino wool comes from Merino sheep and uses extra-fine fibres spun into a soft jersey knit. For underwear, it’s often blended with a little nylon and elastane to boost durability, stretch, and recovery without losing that next-to-skin comfort.
Key benefits
You feel the difference in changing conditions and on days when laundry isn’t guaranteed. Merino balances warmth and breathability while resisting smells that would bench other fabrics.
- Temperature regulation: Feels warm in cooler air and comfortably cool in heat.
- Odour resistance: Natural properties help it stay fresher for longer between washes.
- Moisture management: Moves sweat off skin and handles vapour before it feels wet.
- Soft next-to-skin: Fine fibres reduce itch compared to traditional wool.
- Great for travel: Wear more, wash less without offending your seatmate.
Potential drawbacks
You’ll pay more for quality merino, and it appreciates gentle care to keep it in top form. Some men also find it a touch warm in peak summer heat.
- Higher price tag than basics
- Needs delicate wash care
- Can be too warm on the hottest days
- Not as abrasion-proof as synthetics
- Occasional itch for very sensitive skin
Breathability and moisture control
Merino breathes well and manages both sweat and moisture vapour, keeping you drier than cotton once you’re active. It won’t dry as fast as polyester microfibre, but it maintains comfort across a wider temperature range and resists that damp, clammy feel.
Pouch-compatibility and support
A merino blend with elastane works beautifully in ergonomic pouch designs. The pouch lifts and separates to reduce friction and sticking, while the knit’s gentle stretch provides consistent, non-suffocating support for long days and longer flights.
Care and durability
Wash cold on a gentle or wool cycle with mild detergent, avoid fabric softeners, and line dry or tumble low. Turn inside-out and use a wash bag to limit pilling. Treated well, merino holds shape and feel; high heat and rough laundering shorten its life.
Sustainability and health notes
Merino is renewable and biodegradable. Look for brands that disclose responsible sourcing and animal welfare standards. By helping you stay cooler and drier with reduced friction, merino supports day-long comfort in the groin—something urologists often encourage via supportive, well-ventilated designs.
Best for
If your day spans air-con, outdoors, and everything in between, merino is a reliable all-rounder—especially when odour control matters.
- Variable climates and shoulder seasons
- Travel and repeat wear
- Desk-to-trail days
- Light-to-moderate activity in cooler weather
- Guys prioritising low-odour comfort with natural fibres
4. Cotton: classic, breathable and affordable
Cotton is the familiar favourite in most drawers for a reason: it’s soft, breathable and easy to live with. But when the day heats up or you start moving, its habit of soaking up sweat and staying damp can turn comfort into chafe—so it’s great in the right context, less so in others.
What it is
Cotton is a natural staple fibre spun into yarn and knitted into jersey for underwear. Many modern pairs add a little elastane to boost stretch and help the fabric recover its shape after wear and washing.
Key benefits
For everyday, low-sweat comfort, cotton delivers straightforward, no-fuss wearability at a friendly price.
- Soft and breathable: Gentle on skin with decent airflow.
- Highly absorbent: Feels comfortable while dry.
- Easy care: Washes well without fuss.
- Durable for basics: Handles frequent laundering.
- Budget-friendly: Typically cheaper than premium fibres.
Potential drawbacks
Cotton’s strengths fade once sweat enters the chat, and that’s when issues can creep in.
- Holds onto moisture: Gets clammy in heat or humidity.
- Slow to dry: Stays damp compared with performance knits.
- Can lose shape: Less stretch and recovery than modal or synthetics.
- Higher chafe risk when wet: Damp fabric plus friction equals irritation.
If you want to explore our range, why don’t you take 20% off your first order – use SLY20 at the checkout. Remember you have a ‘first pair guarantee’ as well, so you’ve got nothing to lose.
Breathability and moisture control
Cotton breathes, but it absorbs sweat and retains it. In hot or active conditions it feels wetter, heavier and slower to dry than bamboo viscose, MicroModal or polyester microfibre—so it’s best on cooler days or low-exertion routines.
Pouch-compatibility and support
Cotton works well in pouch patterns for anti-chafe separation, but pure cotton can bag out. A cotton–elastane blend helps the pouch keep its lift and shape so support stays consistent through the day.
Care and durability
Wash warm or cold, avoid over-drying, and you’ll get solid mileage. High heat can shrink cotton and accelerate shape loss; blends with elastane tend to hold up better and look fresher for longer.
Sustainability and health notes
Cotton is a natural, breathable fibre, but conventional crops are resource-intensive. Bamboo-based viscose generally uses less water at the farm stage, which many prefer. From a comfort-health angle, cotton is fine when dry; when damp, chafe risk rises—something a supportive pouch can help mitigate by reducing friction.
Best for
If you want simple, soft and affordable undies for easy days, cotton is a safe bet—especially in a stretch blend.
- Everyday wear in cooler weather
- Low-sweat office days and lounging
- Natural-fibre preference on a budget
- Pouch styles with added elastane for better support
5. Polyester microfibre: quick-drying performance for sport
When you’re racking up kilometres or grinding through circuits, you need undies that move sweat fast and bounce back between sessions. Polyester microfibre is built for that: light, resilient, and engineered to wick and dry at speed so you don’t stay soggy after the hard efforts.
What it is
Polyester microfibre uses ultra-fine synthetic filaments knit into a smooth, lightweight fabric. It’s often blended with elastane for stretch, giving a body-hugging fit that stays put during dynamic movement.
Key benefits
Purpose-made for training and heat, microfibre delivers practical performance gains you can feel mid-workout.
- Rapid moisture transfer: Moves sweat off skin efficiently.
- Dries fast: Minimises post-session clamminess.
- Durable and shape-holding: Stands up to frequent washes and hard use.
- Lightweight feel: Low bulk under gym shorts or tights.
- Supportive with elastane: Keeps everything secure through sprints and lifts.
If you want to explore our range, why don’t you take 20% off your first order – use SLY20 at the checkout. Remember you have a ‘first pair guarantee’ as well, so you’ve got nothing to lose.
Potential drawbacks
The trade-offs show up in day-long comfort and smell management.
- Less natural softness: Can feel slick compared with bamboo or modal.
- Airflow varies by knit: Some versions feel clammy despite being “dry.”
- Can retain odours: Needs prompt washing to stay fresh.
- Petrochemical origin: Not the most eco-forward choice.
Breathability and moisture control
Performance weaves excel at wicking and evaporation, clearly outpacing cotton once you sweat. Pure airflow can lag behind open knits, so the best results come from technical meshes or mapped panels that vent hot zones.
If you want to explore our range, why don’t you take 20% off your first order – use SLY20 at the checkout. Remember you have a ‘first pair guarantee’ as well, so you’ve got nothing to lose.
Pouch-compatibility and support
In a well-cut pouch brief with elastane, microfibre offers firm, bounce-limiting support while separation helps stop stick and rub on high-output days. A slightly longer leg cuts thigh chafe and ride-up during repeats.
Care and durability
Easy-care and tough: machine wash, quick to dry, and resistant to shrinking and bagging out. Expect reliable recovery and fewer saggy waistbands over time than many natural knits.
Sustainability and health notes
Being synthetic, it carries a higher environmental burden than natural fibres. From a comfort-health angle, the fast-dry performance helps reduce prolonged dampness and friction—key to preventing chafe during sweaty sessions.
Best for
- High-intensity training and team sports
- Hot, humid conditions where drying speed matters
- Back-to-back workouts and fast turnarounds
- Guys prioritising firm support and resilience over luxe hand-feel
6. Nylon/elastane blends: lightweight stretch and shape retention
If you’re chasing the best material for men’s underwear when you want a sleek, second-skin fit that won’t sag, nylon/elastane blends are a go-to. Think smooth, low-bulk trunks that move with you and snap back—great under slim trousers and for active days.
What it is
Nylon (a synthetic polyamide) is knitted with elastane (spandex) to create a lightweight, highly elastic fabric. The nylon brings strength and a smooth hand-feel; elastane adds four-way stretch and recovery so the garment hugs and holds its shape wear after wear.
Key benefits
You’ll feel the glide and the support immediately—this combo excels at staying put and looking sharp.
- Four-way stretch and recovery: Maintains a close, supportive fit.
- Lightweight and low-friction: Glides under trousers without catching.
- Quick wicking and drying: Manages sweat better than basic cotton.
- Durable and resilient: Resists bagging out and pilling with proper care.
- Shape retention: Keeps pouch and leg structure through the day.
Potential drawbacks
The trade-off for structure and speed is a touch less “natural” comfort.
- Lower airflow than naturals: Can feel warm in hot weather.
- Odour retention risk: Needs prompt washing to stay fresh.
- Plastic-based: Petrochemical origin isn’t the most eco-forward.
- Feel can be slick/synthetic: Not as plush as bamboo or MicroModal.
Breathability and moisture control
Nylon/elastane wicks and dries quickly, keeping you from staying damp after effort. Pure airflow depends on the knit; some blends can feel “dry but warm,” so they’re best in cool-to-mild conditions or air‑conditioned environments.
Pouch-compatibility and support
This is where the blend shines. The fabric’s snap-back holds an ergonomic pouch contour in place, lifting and separating to cut friction and sticking—exactly the kind of consistent support many clinicians favour for everyday comfort.
Care and durability
Machine wash cold, gentle spin, and line dry or low tumble to protect elastane. Avoid high heat and fabric softeners. Expect excellent shape retention, strong waistbands, and fewer saggy leg openings over time than many natural knits.
Sustainability and health notes
As synthetics, these blends carry a higher environmental footprint than natural fibres. On the comfort-health front, their fast-dry performance and stable support help reduce prolonged dampness and chafe—especially effective in a pouch design.
Best for
If you want a sleek, stay-put base layer with dependable support, nylon/elastane is a smart pick.
- Under slim trousers or uniforms for a no-bulk look
- Gym sessions in air‑conditioned spaces (low-to-moderate intensity)
- Cool-to-mild climates where quick dry matters
- Travel: easy wash, fast dry, minimal wrinkling
- Guys prioritising shape retention and support over ultra-natural feel
7. Silk: featherlight comfort for special occasions
Silk is the indulgent option you pull on when you want that barely‑there feel and a touch of luxury. It’s whisper‑light, naturally smooth against skin, and has a refined drape—perfect under dress trousers or for nights when comfort and finesse matter more than mileage.
What it is
Silk is a natural protein fibre spun by silkworms and woven or knitted into ultra‑fine fabrics. For underwear, it’s prized for its smooth handle and low bulk, delivering a glide-on feel that sits invisibly under tailored fits.
Key benefits
Silk earns its reputation the moment you step into it: soft, sleek, and effortless.
- Featherlight and ultra‑soft: Glides over skin with zero scratch.
- Low bulk under suiting: Disappears under dress pants.
- Naturally moisture‑friendly: Helps move light perspiration off the skin.
- Cool-touch comfort: Feels fresh when you first put it on.
Potential drawbacks
Silk is high‑maintenance and not built for the rough and tumble.
- Fragile and fussy to launder: Needs delicate care.
- Premium price: Costs more than everyday fibres.
- Lower durability: Prone to snags and wear.
- Not for heavy sweat: Better for short, low‑intensity wear.
Breathability and moisture control
Silk handles light moisture well and feels cool at first wear, but it’s not a quick‑dry performer. In sustained heat or high exertion, it can feel overwhelmed compared with MicroModal or polyester microfibre.
Pouch-compatibility and support
Silk’s fluid drape means support depends on cut. An ergonomic pouch will improve separation and comfort, but for firm, all‑day lift you’ll usually get better consistency from bamboo viscose, MicroModal, or technical blends.
Care and durability
Think gentle: cold hand‑wash or delicate cycle in a wash bag, mild detergent, no bleach or softeners, and line dry out of direct sun. Avoid high heat—tumble dryers and hot irons can damage fibres.
Sustainability and health notes
Silk is a natural fibre and skin‑kind. From a comfort standpoint, its smoothness reduces friction points; just remember it’s best for low‑sweat scenarios to keep irritation at bay.
Best for
- Black‑tie, weddings, and date nights
- Under tailored trousers for zero bulk
- Short stints and low‑sweat days
- Gifting or a luxury pair in the top drawer
Final take
If you run cool and dry, almost anything will do. But most guys in Aussie conditions need fabric that keeps sweat moving, feels good all day, and stops chafe. MicroModal is the top pick for hot commutes and long days; bamboo viscose nails everyday softness and breathability (especially with a supportive pouch); merino wins when temps swing and odour control matters; polyester microfibre and nylon blends rule fast-dry sport; cotton is cost‑effective for low‑sweat days; silk is your special‑occasion wildcard.
The bigger unlock isn’t just the fibre—it’s the cut. A well‑designed pouch lifts and separates to prevent skin‑on‑skin friction, which urologists consistently favour for comfort and compliance. If you want that chafe‑free, cooler feel baked in, try a pair of SLY Collective bamboo pouch boxer briefs with the longer leg and ergonomic support. One swap and the midday swamp, ride‑up, and sticking become yesterday’s problems.