The Ultimate Guide to Base Layers for Babies, Toddlers & Children

A good base layer keeps your little one happy, warm and comfortable year-round - in any weather.

In Britain and Northern Europe, cold snaps, wind, rain, frost and even snow can pop up not just in winter, but well into autumn and spring. Dressing your baby or toddler in multiple thin layers is the best way to stay ahead of changing temperatures. Layers trap warm air between them, and you can easily add or remove one as you move between indoors and outdoors.

Why Base Layers Matter for Babies, Toddlers and Children

Newborns & young babies

Newborns struggle to regulate their temperature. Their circulatory system is still developing, and their bodies are small compared with their surface area, meaning they lose heat very quickly. They need a helping hand to stay warm — but not too warm — especially while sleeping.

Older babies, toddlers & small children

They’re a bit better at regulating temperature, but still lose heat twice as fast as adults. Add in puddle jumping, spills, dribble and general adventures, and the challenge becomes keeping them warm, dry and comfortable without bulky layers that restrict movement.

A good base layer is the foundation that helps you get this right.

How to Tell if Your Child Is Warm Enough

Check their core - the back of the neck, tummy or lower back. This should feel nicely lukewarm but not hot.

Hands and feet are not reliable indicators, especially in young babies, whose circulation is still immature.

If you’re outdoors and unsure, use your own comfort level as a guide and adjust based on age:

• Babies under 6 months: dress slightly warmer than yourself

• Babies over 6 months & toddlers: dress similarly to yourself, with extra protection in wet or windy weather

How Thick Should a Base Layer Be?

It depends on the temperature, the child’s activity level, and the season.

• Summer / mild weather: Lightweight Merino 150–200gsm

• Autumn, winter, early spring: Midweight Merino 220–250gsm

• For colder climates: Choose double-knitted Merino (like interlock) for more loft, warmth and insulation. Superlove Merino is a perfectly weighted 240gsm double-knit and if you have ever worn it you'll know why that is the sweet spot.

Plus 230gsm+ Merino doesn’t mean bulky or too hot (thanks to the thermo-genius properties of wool) but in cold weather it makes a difference

Do You Still Need Merino Layers with a Merino Sleeping Bag?

Always a good idea - and especially in winter.

Cotton naturally absorbs moisture (even from the air). When cotton becomes damp, it cools down and can make your baby feel chilly — even inside a Merino sleeping bag.

A Merino base layer worn next to the skin helps maintain a dry, warm microclimate and the wool in the underlayers really works synergistically with a Merino sleeping bag to stabilise temperature all night long.

What to Look For in a Great Base Layer

1. The Perfect Fit

Base layers should be comfortably snug - not tight, not roomy. A close fit traps warm air and prevents draughts. Choose your child’s regular size; they’re intentionally designed to sit closer to the body.

2. Cloud Comfort

Merino is the gold standard for thermal comfort. It’s naturally stretchy, moisture-wicking, quick-drying and truly thermoregulating. No more piling on layers outside only to strip everything off indoors.
Think: climate-controlled cloud comfort.

3. Naturally Breathable

Whether worn for play, sleep or under a Merino sleeping bag, breathability is essential — especially for babies who can’t regulate temperature well.

Merino is the most naturally breathable fibre known, helping prevent overheating and eliminating that clammy, sweaty feel.

Which Fabrics Make the Best Base Layers?

A base layer has two key jobs:

1. Insulation — trapping warm air next to the skin

2. Moisture management — wicking away dribble, spills and splashes so they can’t cause chills

Always choose natural fibres for babies and toddlers.

They breathe, regulate temperature and are far safer next to delicate skin.

Why Merino is best

• Superior insulation

• Exceptional moisture wicking (keeps skin dry)

• Unmatched breathability

• Naturally fire-resistant (ideal for sleepwear)

• Stays warm even when damp

• Dries quickly

• Extremely soft and gentle on sensitive skin

• Helps improve sleep (yes — it’s backed by studies)

Why cotton isn’t ideal for cold weather

Cotton is soft and breathable, but:

• it absorbs moisture and stays damp

• becomes heavy and cold when wet

• offers limited insulation in cold conditions

Why synthetics should be avoided for babies

They don’t breathe well, trap heat and moisture, can cause overheating and clammyness, and are often highly flammable unless chemically treated with nasty stuff.
(Save those for sweaty adults who want a strongly wicking base layer… and don’t mind smelling a bit to get it)