Why the ONE Shirt Is the Best Base Layer for Kids (And How to Layer It Year-Round)

I didn’t set out to make just another kids’ shirt.
I wanted to make the shirt, the one that works for everything. The one that stays at the top of the laundry pile because it’s always the first thing your you and your kid grabs.

That’s how the ONE bamboo sun shirt came to life: one shirt that keeps kids warm, cool, protected, and comfortable in any season.
Here’s why it works, and how to layer it for year-round adventure.

What Makes the Perfect Base Layer

A good base layer should:

• Regulate temperature (warm when it’s cold, cool when it’s hot)
• Wick moisture away from the skin
• Dry fast after activity or washing
• Fit comfortably without being tight or itchy

The ONE Shirt was engineered around these principles using our signature bamboo viscose blend. It’s soft, breathable, and naturally UPF 50+. That means it functions as both a sun shirt and a thermal base layer, depending on the season.

Unlike synthetic base layers that trap odor or cause irritation, bamboo stays fresh and gentle, perfect for kids with sensitive skin.

Winter: Warmth Without Bulk

In cold weather, the ONE Shirt acts as the first line of defense against chill, and a barrier against itchier but warmer fabrics.
Pair it with:

• A mid-layer (like fleece or wool) for insulation
• A windproof or waterproof outer layer for protection

It won’t bunch under jackets or feel restrictive, and has thumbholes for easy layering
We use it for:

• Ski days (as a moisture-wicking base layer)
• Camping nights (soft sleep layer)
• School mornings when temperatures dip

Summer: Breathable Sun Protection

When temperatures rise, the same shirt transforms into a lightweight, UPF 30+ sun shirt.
It shields against UV rays while allowing airflow to keep kids cool and dry.

We wear it for:

• Hiking, fishing, and beach days
• Long car rides when sunscreen feels sticky

It’s also odor-resistant, so you can pack fewer pieces, perfect for minimalist travel. 

Spring and Fall: The Versatile Middle Ground

During shoulder seasons, the ONE Shirt handles unpredictable weather like a pro.
Layer under a vest, pair with joggers, or use as pajamas on camping trips.
It’s the piece that goes from muddy play to bedtime without changing outfits.

Fabric Science: Why Bamboo Wins

Bamboo viscose has natural thermal-regulating properties, meaning it keeps your child’s body temperature balanced whether it’s hot or cold.

It’s also:

• Hypoallergenic and breathable for sensitive skin
• Moisture-wicking (pulls sweat away fast)
• Odor-resistant for multi-day adventures
• Silky soft and tag-free for sensory comfort

For kids with eczema or sensory sensitivities, it’s a base layer they’ll actually want to wear.

Care Tips to Keep It Performing Like New

• Wash cold, hang dry or tumble low
• Skip fabric softeners and bleach
• Avoid rough Velcro that can snag fabric
• Hang in the closet to keep wrinkle free

Proper care helps maintain the integrity of the bamboo fibers and UPF protection.

From Backyard to Base Camp

Whether you’re sledding, hiking, or camping under the stars, the ONE Shirt replaces a closet full of “specialized” gear.
One shirt, every adventure.

We built it because families shouldn’t have to choose between comfort, protection, and simplicity.

Love,
Adriana
Founder of Play Outside