Cotton vs. Lyocell in the Sauna: Which Fabric Performs Better in Heat and Water?

Natural fibres are increasingly replacing conventional synthetic fabrics in activewear and swimwear. But not every natural or plant-derived fibre behaves in the same way, particularly in a sauna, where a garment is exposed to heat, perspiration, humidity and water in quick succession.

Cotton is often recommended for the sauna because it is breathable, familiar and comfortable against the skin. Lyocell offers many of the same qualities, but its particular moisture-management and wet-performance properties can make it better suited to close-fitting sauna swimwear.

So, what is the difference between cotton and lyocell and why did we choose lyocell for Saade?

Cotton is comfortable but highly absorbent

Cotton is a natural fibre known for its softness, breathability and ability to absorb moisture. These qualities make it a popular material for sauna towels, robes and loose-fitting garments.

Absorbency, however, is not always the same as moisture management.

Cotton readily takes up sweat and water. In a towel, this is exactly what you want. In a close-fitting swimsuit, it can mean that the fabric becomes increasingly saturated, feels heavier and remains wet against the body for longer.

That does not make cotton unsuitable for every form of swimwear. Cotton-rich bikinis can work particularly well when they are lightly constructed, adjustable and intended for relaxed beach use. However, a fitted sauna swimsuit has a different job to do.

It must remain comfortable and secure while moving between:

• dry sauna heat;
• perspiration and humidity;
• cold showers or plunge pools;
• swimming pools or natural water;
• and the cooling-down period afterwards.

How is lyocell different from cotton?

Lyocell is a cellulosic fibre made from wood pulp. Like cotton, its principal raw material comes from plants. Unlike cotton, the cellulose is dissolved and regenerated into a smooth, controlled fibre.

This structure gives lyocell a particularly soft surface and strong moisture-regulating properties. Lyocell fibres can absorb moisture into the fibre structure, helping to support a more comfortable and less clammy feeling next to the skin.

Lyocell is also known for retaining relatively good strength when wet: an important consideration for garments that repeatedly move between dry and saturated conditions.

The exact performance of any textile always depends on more than its fibre content. Fabric weight, knitting structure, lining, stretch and garment construction all influence how it behaves. But lyocell gives us a strong foundation for designing a swimsuit specifically for sauna use.

Cotton and lyocell in sauna conditions

Breathability

Both cotton and lyocell are breathable cellulosic fibres. They are generally more comfortable in heat than conventional swimsuit fabrics made primarily from polyester or polyamide.

For a sauna garment, however, breathability must be combined with effective moisture control. The objective is not simply to absorb sweat, but to manage it while maintaining comfort against the skin.

Lyocell was selected for Saade because it offers the natural, breathable feeling we wanted while supporting moisture regulation in a close-fitting garment.

Feeling when wet

Cotton can hold a considerable amount of water. As it becomes saturated, a cotton garment may feel heavier and cling more noticeably to the body.

Lyocell is also absorbent, but its moisture interaction and smooth fibre surface can help provide a more comfortable next-to-skin feeling. This is especially relevant when moving directly from the sauna into a shower, plunge pool or swimming pool.

Shape and recovery

Neither pure cotton nor pure lyocell naturally provides the stretch and recovery required from a fitted swimsuit.

This is why many so-called natural swimsuits still contain a small percentage of elastane. The elastane helps the garment stretch around the body, remain secure in water and return to its original shape after use.

Saade’s fabric combines 88% lyocell with 12% recycled elastane. The lyocell provides softness, breathability and a predominantly plant-derived base, while the elastane provides the stretch and recovery needed for reliable swimwear performance.

Drying and post-sauna comfort

No absorbent cellulosic swimsuit will dry as rapidly as an ultralight synthetic performance fabric under every condition.

However, drying speed is not determined by fibre alone. Fabric thickness, construction, air circulation and the amount of water retained all play important roles.

For sauna wear, our priority was to create a material that balances moisture management, skin comfort, coverage and water performance, not simply the fastest possible drying time.

As with all swimwear, the garment should be rinsed after use and allowed to dry completely rather than being left damp in a bag.

What about bacteria?

Warmth, moisture, perspiration and skin oils can create conditions in which microorganisms multiply on textiles. This is relevant to any damp garment, whether it is made from cotton, lyocell or synthetic fibres.

It would therefore be misleading to say that cotton automatically “breeds bacteria,” or that all lyocell is naturally antibacterial.

What matters is how effectively the specific fabric manages moisture, how long it remains damp, whether it has been independently tested for antibacterial performance and how the garment is cared for after use.

Saade’s finished fabric has been selected and tested for its intended application. Any antibacterial statement we make refers to the performance of our specific fabric—not to every lyocell textile in general.

Is cotton good for the sauna?

Yes, in the right form.

Cotton remains an excellent choice for:

• sauna towels;
• robes;
• loose wraps;
• pareos;
• and lightweight clothing worn before or after a sauna session.

A cotton-rich bikini may also be suitable for relaxed sauna and beach use, depending on its construction.

But when designing a fitted garment expected to perform in both intense heat and water, we believe lyocell offers a better balance of softness, breathability, moisture regulation and wet strength.

Why Saade uses lyocell

Most conventional swimwear is made almost entirely from synthetic fibres. We wanted to substantially reduce that reliance without sacrificing the security and functionality expected from a swimsuit.

Our solution is not to pretend that stretch can currently be achieved without any synthetic component. It is to use synthetics only where they perform an essential function.

Saade swimwear is made from:

88% lyocell for softness, breathability and moisture management

12% recycled elastane for stretch, shape retention and water performance

The result is a predominantly plant-derived swimsuit designed specifically for the transitions that define modern sauna culture: from heat to water, from perspiration to immersion, and from sauna to cool-down.

The conclusion: cotton or lyocell?

Cotton and lyocell are both valuable alternatives to predominantly synthetic textiles, but they are not interchangeable.

Cotton excels in absorbent, loose and relaxed sauna essentials. Lyocell offers properties that are particularly useful in close-fitting garments exposed to repeated heat, moisture and water.

For a towel, we would choose cotton.

For a sauna swimsuit, we chose lyocell.