Bamboo, cotton, modal — what actually goes on baby skin

You're standing in the baby section of a store, or you're three browser tabs deep, and every label says something slightly different. "100% cotton." "Organic cotton." "Bamboo viscose." "Modal." "Tencel-blend." None of them tell you what's actually different in the hand-feel, on the skin, or in the wash. So we wrote the comparison we wished existed.

Quick framing: all three of these are fine fibers for babies. There's no villain in this story. But there are real differences in how they feel, breathe, wear, and age — and once you know the differences, the right pick gets obvious for your baby.

Cotton

Cotton is the default for a reason. It's affordable, durable, easy to wash, and most babies do fine in it. Organic cotton (look for GOTS certification) skips the heaviest pesticides, which matters more for the planet than for the skin once the fabric reaches you.

Where cotton struggles: sweat. Cotton holds water against the skin instead of moving it away. For a baby who runs warm at night (basically all of them), that means a damp pajama by 4am and an early wake. The fiber itself, viewed under a microscope, has tiny rough edges — fine for typical skin, sometimes a problem for eczema-prone babies.

Modal (and Tencel)

Modal is bamboo's first cousin — both are regenerated cellulose fibers, meaning plant pulp turned into smooth thread through a closed-loop chemical process. The difference is the source: modal comes from beech tree pulp, bamboo viscose from bamboo pulp.

Modal feels almost identical to bamboo on the skin. It's silky, drapes well, breathes, and wicks moisture far better than cotton. It also tends to hold its shape through more washes — modal blends are a real workhorse. The catch: modal isn't quite as stretchy as bamboo viscose, so for fitted sleepwear (like footie pajamas, where stretch helps the snug fit) bamboo wins on comfort.

Bamboo viscose

Bamboo viscose has the smoothest fiber cross-section of the three. That's not marketing language — it's literally measurable under a microscope. The smoother the fiber, the less mechanical friction on skin, which is why it's the fabric most often recommended for eczema-prone babies.

Practical advantages: 3–4× better moisture wicking than cotton, naturally cooling in summer, naturally insulating in winter (a paradox we don't fully understand but consistently observe), and stretchy enough to keep snug-fit pajamas comfortable. Downsides: bamboo viscose pills a little more than cotton if washed roughly, and it costs more. We think both are worth it.

Side-by-side

If you read nothing else, read this:

• Softness on day one: bamboo > modal > cotton
• Softness after 50 washes: modal > bamboo > cotton
• Moisture wicking: bamboo ≈ modal >> cotton
• Durability over years: cotton > modal > bamboo
• Stretch (fit for snug sleepwear): bamboo > cotton (with spandex) > modal
• Eczema-friendly: bamboo ≈ modal > cotton
• Cost: cotton < modal < bamboo

Our pick (and why)

We landed on a 95% bamboo viscose / 5% spandex blend for everything we make. The bamboo gets us the smooth, low-friction skin feel and the moisture wicking. The spandex gets us the snug, safe fit that U.S. flammability standards require for sleepwear without flame retardants. Modal would also work — we'd happily wear it on ourselves — but for a baby who's growing fast and sleeping in their clothes 12 hours a day, bamboo's stretch wins the day.