The Science Behind Kids’ Curly Hair
makes kids’ curly hair do its magical, sometimes maddening thing. Here’s the real, rooted science — broken down with clarity, a little flair, and zero fluff:
Let’s go…
1. It Starts in the Genes
Curly hair is inherited — it’s a family heirloom wrapped in keratin.
Hair texture is controlled by a mix of multiple genes from both parents, not just one “curly gene.”
- If both parents have curls, chances are high their child will too.
- Even if only one parent has curls, it can still pop up—sometimes skipping a generation like a mischievous cousin.
Key Players:
- Gene variants like TCHH (trichohyalin) and WNT10A are involved in follicle shape and hair structure.
- These determine whether your hair grows straight, wavy, curly, or coily.
2. Follicle Shape = Curl Pattern
The shape of the hair follicle is the main reason hair curls (or doesn’t).
| Follicle Shape | Hair Type |
|---|---|
| Round | Straight |
| Oval | Wavy |
| Flat/elliptical | Curly/Coily |
Curly hair literally grows out of the scalp in a curl — it’s not straight hair that just bends.
3. Keratin + Disulfide Bonds = Structure
Hair is mostly made of keratin, a strong protein, and its shape is held together by chemical bonds:
- Disulfide bonds (the strong ones): More of these = tighter curls.
- Hydrogen bonds (the weak ones): These break and reform with water. That’s why wetting hair or humidity affects curl shape temporarily.
So when your kid’s hair gets frizzy in the rain?
Blame the hydrogen bonds going rogue and reshaping the curl pattern.
4. Porosity = How Hair Drinks Moisture
Kids’ curls often have higher porosity, especially if hair is fine or mixed-textured.
This means:
- The cuticle (outer layer of the hair strand) is more open.
- Moisture goes in fast… and escapes just as quickly.
- That’s why curly hair dries out faster and needs regular hydration.
Over time, porosity can change — from age, product buildup, even hard water.
5. Kids’ Hair Is Still Developing
Kids under 6 or 7 often have “baby texture” hair — softer, finer, with a looser curl pattern.
- Curls can tighten, change, or even shift type completely around puberty.
- Hormonal changes affect the scalp’s oil production and hair’s structure.
- That’s why hair routines may need adjusting as they grow.
6. Scalp & Oil: It’s a Dry Game
Sebum (your scalp’s natural oil) struggles to travel down curly strands because of the spiral structure.
- Straight hair: sebum slides down = shiny, greasy faster
- Curly/coily hair: oil gets caught in the curls = drier ends
This is why curly kids need added moisture — conditioners, leave-ins, and oils that mimic what their scalp can’t distribute fast enough.
7. Why Curly Hair Loves ‘Slip’
When wet, curly hair tangles like vines in a rainforest.
- This is because the twists and curves interlock easily.
- Add to that friction from brushing or rough drying, and you get breakage.
Conditioners with “slip” (slippery ingredients like glycerin, aloe vera, or behentrimonium methosulfate) reduce that friction so curls slide instead of sna
How kids’ curls change over time
Spoiler: baby curls lie. Many kids start out with soft wisps or ringlets that evolve completely by age five. Puberty? Another plot twist. Be ready to adjust your approach as their hair matures — what worked at 4 may not cut it at 9. Flexibility is part of the job.
Curl typing (wavy, curly, coily: Types 2A–4C)
Not all curls are created equal. Type 2 waves are loose and beachy, Type 3 curls spiral and bounce, and Type 4 coils? Glorious zigzags of tight texture. Knowing your kid’s curl type helps you pick products and routines that actually work — no more guessing games. Remember: they might even have more than one type on their head.
Porosity basics (low, medium, high)
Porosity tells you how well their hair holds moisture. Low porosity means the cuticle is tight — water rolls right off. High porosity means the hair soaks up everything but loses it fast. There’s a quick test: drop a clean strand into a glass of water. Sink = high. Float = low. In-between = medium. This one tip will save you so much product grief.
Density and texture
Density = how much hair is packed onto their scalp. Texture = how thick each individual strand is. Your kid might have fine, dense curls or thick, sparse coils. This matters because it changes how you style, detangle, and protect those strands. It’s not just about curl pattern — it’s about the whole picture.
Density: How Much Hair Is Actually on Their Head?
Let’s get one thing straight: density has nothing to do with how tight the curls are.
You can have tight coils and still not have a lot of hair on your head.
You can also have loose waves that are thick as a lion’s mane.
It’s not the shape of the strands — it’s how many are packed onto that scalp.
Think of it like this:
If curl pattern is the shape of the strand, density is the crowd it rolls with.
Here’s how to break it down:
Low Density (a.k.a. Less Hair Per Square Inch)
You can easily see your child’s scalp when the hair is parted.
Styles may look a little more “airy” or soft.
These curls can look flat or stringy without the right care — and can be overwhelmed by heavy products.
💡 Pro Tip: Light, liquidy leave-ins and mousses are your friend. Too much cream can make it look limp.
Medium Density
Scalp is visible only when parted, not through the hair itself.
It holds styles fairly well, and responds predictably to products.
The Goldilocks of density — not too thick, not too thin.
💡 Pro Tip: You’ve got flexibility here. Experiment to see what works — just don’t assume one-size-fits-all.
High Density (a.k.a. Hair for Days)
We’re talking thick, lush, full-on volume.
Parting takes effort. Braiding takes stamina. You may need a break and a snack halfway through.
💡 Pro Tip: Heavier creams, curl butters, and defining gels can help clump and define curls without puffing out. Sectioning is essential — don’t try to tackle it all at once.
Why It Matters:
Product choice, styling routines, and detangling strategies all shift depending on density.
Two kids might have the same curl type (say, 3B), but one with high density will need way more product — and patience — than one with low density.
Understanding density helps you avoid overload… or under-care.
And remember: density can change over time. As your child grows, hormones, health, and even seasonal changes can affect it.
Texture: The Feel of the Strand, Not the Shape of the Curl
You might think texture is about curl pattern, but nope.
Texture is how each strand feels between your fingers.
It’s the difference between silk and cotton, floss and rope, fairy hair and lion mane.
It’s about the diameter of each strand — not the style it’s twirling in.
Let’s break it down:
Fine Texture (a.k.a. Fragile as Fairy Wings)
These strands are thin and delicate — sometimes hard to see.
They tangle like nobody’s business and snap if you so much as look at them wrong.
Traits:
- Can get weighed down by product easily
- Looks wispy or see-through when wet
- Often shines easily, but lacks volume
💡 Handle With Care:
Gentle detangling only, minimal product, and avoid tight styles.
Stick with lightweight creams or milks.
This hair needs kindness, not control.
Medium Texture (a.k.a. The Middle Child Who’s Surprisingly Low Drama)
Not too fine, not too coarse — this hair is the most “go with the flow.”
It holds styles, handles detangling well, and generally plays nice.
✨ Traits:
- Visible strand width, but not wiry
- Can handle a range of products
- Responds predictably to moisture and styling
💡 Style Smart:
You’ve got options! Go light or go creamy — just don’t overload it.
Still treat it gently, but it won’t freak out if you skip a step now and then.
Coarse Texture (a.k.a. Strong Like a Superhero Cape)
These strands are thick and strong — you can feel them in your hands.
They resist heat, hold styles, and soak up product like a sponge.
✨ Traits:
- Feels rougher or wiry to the touch
- Prone to dryness
- Can look frizzy or undefined without enough moisture
💡 Feed the Beast:
This hair LOVES moisture. Think rich butters, deep conditioners, and thick creams.
Don’t be afraid of oils and heavy stylers — they’re not enemies here.
Just make sure you rinse and clarify occasionally so it doesn’t build up.
Why Texture Matters:
Knowing your child’s texture helps you avoid the dreaded product mismatch.
Fine strands can drown in heavy butters. Coarse ones will laugh at your lightweight mist and stay dry anyway.
And remember: texture + density + curl type = the full hair picture.
Think of it as a hair care equation. Miss one piece, and things get frustrating fast.
You’re not just working with curls — you’re working with a whole little hair ecosystem.
Learn it. Love it. Grow with it.
How Often Should You Wash?
Most kids with curls do not need shampoo every day.
Let’s clear this up straight away:
Your kid’s hair is not dirty.
It’s just curly.
And curls don’t want to be squeaky clean. They want to be moisturised, respected, and left the heck alone most days.
“Squeaky Clean” is a Lie
That squeaky feeling after a shampoo? Yeah, that’s the sound of all the moisture being snatched out of the strands like joy from a Monday morning. Curly hair thrives with natural oils—strip them, and you get frizz, breakage, and drama.
Washing Routines: One Size Does Not Fit All
Curly routines depend on:
- Age
- Curl type
- Lifestyle (Are they rolling in mud or just drawing on the walls?)
- Toddlers (1–3): Once a week max
- Once a week is enough. Seriously. They’re not working in a coal mine.
- Co-wash (conditioner-only wash) or a gentle cleanser with no sulfates.
- Keep it fun: sing, splash, let them “help.”
- Young kids (4–7): Every 5–7 days
- 1–2 washes per week. Add more if swimming or sweating lots.
- Use a sulfate-free shampoo every other wash.
- Alternate with co-washing if the scalp isn’t grimy.
- Tweens (8–12): Every 4–6 days (or as needed for scalp)
- They’re experimenting, hormonal, maybe even self-conscious. That’s normal.
- Let them learn what feels good for their scalp.
- Introduce clarifying shampoo only once a month if product buildup is real.
- Teach about moisture balance—too much washing = thirsty hair.
Goodbye, Sulfates 👋
Ingredients to Love
Aloe vera, glycerin, chamomile, coconut oil, shea butter.
Ingredients to Avoid
That pastel-coloured, cartoon-covered bottle may say tear-free, but check the label. If it’s got:
Drying alcohols (think alcohol denat, ethanol) — brittle-city
Sulfates (like sodium lauryl sulfate) — strip moisture
Parabens — questionable stuff, often unnecessary
- Sodium Lauryl Sulfate
- Ammonium Lauryl Sulfate
- Alcohols (like SD alcohol, not the good fatty ones)
Co-Washing vs. Shampoo: What’s the Deal?
Co-washing = using a conditioner to cleanse the scalp. Sounds wild, but it works wonders on curls that hate being stripped.
- Great for dry, coarse, or tightly curled hair.
- Use a lightweight conditioner with slip (aka, it makes detangling easier).
- Still scrub the scalp gently—co-wash doesn’t mean don’t clean.
- Shampooing has its place:
- After swimming in chlorine
- When there’s product buildup
- When the scalp is itchy or flaky
Pro tip: Always follow shampoo with a deep, hydrating conditioner. Shampoo opens the door. Conditioner brings the good stuff in.
PSA: Tear-Free Doesn’t Always Mean Curl-Friendly
Those baby formulas might be “gentle on eyes,” but they’re often harsh on hair. They’re not built for texture, kinks, coils, or anything with volume.
Don’t feel guilty if you’ve been using them—we all started somewhere. Just swap when you can. Your kid’s curls will thank you. Eventually. Probably with less crying at bathtime.