Why Babies’ Hair Colour Changes: A Doctor’s Science-Backed Guide

A recent paediatric explanation about why babies’ hair colour often changes after birth has left many parents nodding along in recognition. If your newborn arrived with a head of raven-dark fuzz that lightened to sandy blond by their first birthday—or the reverse—you’re not imagining it. The science of melanin (the pigment that colours hair, skin and eyes), genetics, and early-life hair cycles all play a role. Here, we unpack the biology behind baby hair colour, what’s normal, what to expect across the first two years, and how to care for delicate infant hair without interfering with nature’s plan.

What determines a baby’s hair colour at birth?

Hair colour is governed by melanin—the same pigment responsible for skin and eye colour. Two main types matter for hair:

• Eumelanin: Produces brown to black tones. More eumelanin typically means darker hair.
• Pheomelanin: Produces red and golden tones. Higher proportions tilt hair towards strawberry, copper, or warm blond shades.

At birth, melanin production in hair follicles is still calibrating. Several factors explain the ‘surprise shade’ you might see in the delivery room:

• Foetal hair types: Babies grow ultra-fine lanugo in the womb (usually shed before birth), followed by soft vellus hair. These early fibres can appear darker because they’re fine and packed densely, or lighter because they’re translucent.
• Transitional physiology: Pigment cells (melanocytes) are present but not at full output. What you see on day one isn’t the final word on colour.
• Genetic variation: Hair colour is a polygenic trait. Multiple genes influence how much eumelanin versus pheomelanin a follicle makes—and that output can shift as a child grows.

Why baby hair often changes in the first year

It’s common for newborns to shed some or all of their first hair, a normal process called telogen effluvium that can occur around two to six months. This isn’t the same as adult hair loss; it’s a reset as follicles synchronise their growth cycles. When new hair grows back, the colour and texture can differ from what you saw at birth.

Several overlapping factors drive the change:

• Melanin ‘switching’: As follicles mature, melanocytes can increase eumelanin or pheomelanin output, shifting hues from darker to lighter or vice versa.
• Postnatal hormones: Hormonal changes after birth influence follicle activity, including pigment production.
• Sun exposure: UV light can gradually lighten hair, especially in infants with low eumelanin. This effect is cumulative but gentle—think highlights rather than dramatic bleaching.
• Texture evolution: Baby hair is typically finer and silkier. As thicker, more pigmented terminal hairs replace it, colour can appear richer or deeper even if melanin levels only change slightly.

Typical timeline (every child differs):

• 0–3 months: Birth colour is a placeholder; fine fibres may appear darker or lighter than they’ll be later.
• 3–6 months: Shedding of newborn hair; sparse patches and hairline changes are common.
• 6–12 months: Regrowth with evolving shade; some babies shift multiple tones within this window.
• 12–24 months: Colour trends become clearer, though subtle changes can continue into early childhood.

Genes, melanin and the environment: what really decides the final shade?

While parents often search newborn photos for clues, the eventual hair colour reflects a complex interplay between genetics and biology. Multiple genes influence melanin type and quantity, and the cumulative effect can produce a wide spectrum of colours. That’s why two dark-haired parents might have a fair-haired toddler—or vice versa—especially if lighter or red hair occurs elsewhere in the family tree.

Beyond genes, these factors also influence how colour appears:

• Hair diameter: Thicker fibres tend to look darker and more opaque than ultra-fine baby strands, even with similar pigment levels.
• Density and length: As hair fills in and grows longer, it can appear deeper in tone.
• Seasonal effects: Sunlit summers may bring temporary lightening; winter regrowth can read slightly darker.
• Health and nutrition: Adequate nutrition supports overall follicle function. In typical, healthy infants, standard feeding (breastmilk or formula) is sufficient for normal hair development.

Crucially, these changes are gradual and benign. A baby’s evolving hair shade is part of normal development rather than a sign of deficiency or damage.

How to look after baby hair while nature decides

You can’t (and shouldn’t) control melanin, but you can create a gentle environment for healthy growth as your child’s hair journey unfolds.

• Go gentle with washing: Cleanse with lukewarm water and a mild, fragrance-free baby wash when needed. Over-washing can dry delicate scalps.
• Skip tight styles: Avoid tight bands or clips that may tug on fine fibres. Opt for soft, loose accessories and minimal tension.
• Use a soft brush: A baby-safe, soft-bristle brush or your fingertips help lift cradle-cap scales gently; don’t scrape.
• Protect from harsh sun: A brimmed hat and shade are kinder than relying on product; this also limits UV lightening and protects the scalp.
• Keep products simple: No dyes, bleaches, or adult-strength treatments. Baby hair doesn’t need styling chemicals to look its best.
• Patience over predictions: Resist trying to ‘lock in’ a shade with early haircuts or routines. Trims don’t change follicle pigment programming.

If your infant has a dry scalp or cradle cap, gentle emollients and careful brushing can help. However, persistent redness, swelling, or significant discomfort warrants a conversation with your health visitor or GP.

When a change in colour might need a second look

Most colour shifts are normal, reflecting melanin adjustments and routine shedding/regrowth. Still, it’s sensible to seek advice if you notice:

• Sudden, patchy hair loss with redness or scaly, inflamed skin.
• Very brittle hairs that break easily accompanied by scalp irritation.
• Unexpectedly stark colour changes alongside changes in skin pigment or overall health.

These situations are uncommon and often manageable, but they’re worth a professional opinion for peace of mind.

Key Takeaways

• Newborn hair colour is a starting point, not the final shade; melanin levels and hair type evolve through the first two years.
• Early shedding and regrowth are normal; the second wave of hair may differ in colour and texture.
• Sunlight, hair thickness, and density can subtly shift how colour appears without changing genetics.
• Gentle care—minimal tension, mild washing, and sun protection—supports healthy infant hair and scalp.
• Seek advice if colour changes coincide with scalp inflammation, discomfort, or sudden patchy loss.

Frequently Asked Questions

When will my baby’s ‘true’ hair colour show?
Many parents start to see a clearer trend by 12–18 months, though subtle shifts can continue into early childhood. There’s no precise deadline—genetics and follicle maturation move at individual paces.

Can bath products change my baby’s hair colour?
No. Gentle baby shampoos don’t change melanin. Over-washing can make hair look dull or dry, but it won’t turn dark hair blond or vice versa.

Does cutting my baby’s hair affect the final colour?
No. Trimming doesn’t influence follicle pigment production. It can make hair look thicker as ends blunt, but the colour is set by melanin inside the follicle.

Why did my baby’s dark newborn hair fall out and grow back lighter?
Newborn shedding followed by regrowth is normal. As follicles mature, melanocytes may produce less eumelanin or more pheomelanin, revealing a lighter or warmer shade.

Can sun exposure change a baby’s hair colour permanently?
Sun can temporarily lighten hair, especially fine, light fibres. However, regrowth typically reflects the follicle’s programmed pigment, not the sun’s cosmetic effect.

Is there a link between eye colour and hair colour changes?
Both involve melanin and can evolve during infancy. However, they’re influenced by different gene sets, so one doesn’t strictly predict the other.

Could sudden colour changes signal a health issue?
Most shifts are benign. If you notice rapid, patchy loss, scalp inflammation, or systemic symptoms, seek guidance from your health visitor or GP.

My baby’s hair is reddish in sunlight but brown indoors. Which is ‘real’?
Lighting and fibre diameter can change perception. As hair thickens, the underlying blend of eumelanin and pheomelanin becomes more apparent in consistent lighting.