Published on May 27th, 2020
You’ll never forget the moment your baby first saw you, really saw you. Did a big smile scrunch his cheeks up around his eyes? Did her big baby blues go wide with interest and excitement? A child’s eyes are enchanting little pools of wonder and expression. You’ve probably spent hours just watching your child’s gaze as it takes in every detail of their new world.
And you’ve probably done a little wondering yourself, asking “Will my baby’s eyes stay blue?”
Your child’s eye color isn’t set in stone. In fact, only one in five Caucasian newborns retain their newborn blue eyes into adulthood. So, will your child’s eyes keep their periwinkle twinkle? Or will there be exciting new changes to come?
How Eye Color Works
Whether your babies’ eyes stay blue depends on the structure of the eye itself. For those of you who were spaced out during 7th-grade biology, here’s a crash course in eye terminology:
- Melanin – Melanin is a brown pigment found in skin, hair, and eyes that absorbs UV light and radiation. It’s produced in cells called melanocytes and the production is stimulated by light. This is why your skin “tans” in the sun—more melanin is being produced.
- Melanocytes – Everyone has a similar number of melanocytes, but some people’s melanocytes produce more melanin than others. High-producing melanocytes result in darker skin, hair, and darker eye color. And whether melanocytes are high-producing or low-producing is determined by genetics.
- Iris – A great song by the Goo Goo Dolls and the colored part of the eye. It’s a structure of muscles and cells that contracts and relaxes to let light through the pupil—the black center of the eye. The structure of the iris is made of two layers.
- Pigment Epithelium – The back layer of the iris, the pigment epithelium is composed of a single layer of cells and contains melanin. Even if you have blue eyes, you have melanin in your pigment epithelium.
- Stroma – The stroma is the front layer of the iris. It’s composed of overlapping fibers and cells and contains a varying amount of melanin depending on the individual. Think of it like stained glass layered on top of the darker pigment epithelium. The amount of melanin in this part of the eye is what affects eye color (discussed further below).
What Makes Up Eye Color?
How much melanin there is in the stroma is the dominant factor in eye color.
- Brown eyes: As mentioned earlier, eyes that have large amounts of melanin in the stroma appear brown because melanin absorbs the UV light. This gives them the darker hue.
But that doesn’t explain one thing: If the eye has no melanin in the stroma to absorb light and create a darker color, why do eyes look blue?
- Blue eyes: The blue hue comes from the structure of the iris and a property of light captured in the Tyndall Effect. When light enters the iris (the structure of muscles and cells), the light waves are scattered. The resulting effect is the shorter wavelengths (blue end of the light spectrum) is reflected out. Viewers then observe the eyes as blue.
There can be varying amounts of melanin within the eye’s stroma, and the structure of the eye isn’t the same across all people. That’s why no two eyes look exactly the same. It’s also why there’s a whole spectrum of eyes that appear hazel and green.
- Hazel and green eyes: When there’s some melanin in the stroma, but not enough to absorb all of the UV light coming in, this results in a combination of blue hue (from the iris) and brown tint (from the melanin). The result? Eyes that appear green, amber, and hazel.
Wait! Where Do Genetics Come In?
Genetics do play a role in eye color, although it’s not as simple as “dominant” and “recessive” genes (something that’s been incorrectly taught in schools for the past hundred years). Genes determine the amount of melanin production in the stroma, which is the most telling factor of whether eyes will be on the blue or brown side of the color spectrum.
Many genes are involved in melanin production. Scientists have found one region of chromosome 15 which might hold the key to eye color. Specifically, two genes found close to one another, labeled OCA2 and HERC2, are of particular importance.
- OCA2 – The OCA2 gene is responsible for the protein production of the P protein. The P protein matures the melanosomes in the eyes. Melanosomes are the organelle (within melanocyte cells) where melanin is produced. Less P protein means less melanin, which results in irises on the blue side of the spectrum.
- HERC2 – The HERC2 gene is responsible for turning on and off the OCA2 gene. So, while the OCA2 gene could be maturing melanosomes normally, HERC2 could turn this gene off, resulting in less melanin.
While these two are particularly telling, there’s still much work to be uncovered about which genes play a role in determining eye color. As of now, there are more than a dozen genes that are reported to have some role in a person’s twinkle.
Why Does a Baby’s Eye Color Change?
There’s one thing to remember about melanin: the production of melanin is stimulated by light.
For nine months, your growing baby was away from the biggest melanocyte stimulant that exists—the sun! Since there’s definitely no skylight in mom’s womb for baby to catch some rays, there’s a chance that the melanocytes have been dormant.
Over time, as your baby basks in light, their melanocytes go into normal production mode. As the melanocytes begin producing melanosomes which create the melanin, your child’s true, beautiful eye color will shine through. And while they may have started with blue eyes, that could mean a change to green, hazel, or brown eyes.
How Long Do Babies’ Eyes Stay Blue?
If blue eyes are built into your baby’s DNA, they’ll be blue-eyed for life. What this means is that the genes that produce melanocytes and melanosomes—which ultimately create the melanin—need to be “written into the genetic code” from the get-go.
If the genes have already determined that no melanin will be produced, your baby’s eyes will stay blue. If the melanocyte stimulation hasn’t started because there’s been no light, then your baby’s blue eyes might start to change within six months to three years.
In rare cases, your child’s eyes may change up to the age of six. However, on average, by the time your baby blows out their first birthday candle, they will have their permanent eye color. (Well, you might have to blow it out for them, but you get the picture.)
The eye color change is gradual. You may not even notice the different color of your child’s eyes at first. But one day, you’ll wake up from a mommy-baby nap to find a green-eyed toddler blinking back at you.
Dominant and Recessive Genes: Debunked
Mentioned above, the idea of dominant and recessive gene traits has long simplified how eye color works. The thought was:
- Eye color is determined by two alleles (gene variants).
- Brown is a dominant allele (B). Blue is a recessive allele (b).
- For a person to have blue eyes, they need two recessive alleles (bb).
- For a person to have brown eyes, they need at least one dominant allele (Bb or BB).
This stipulated that if two blue-eyed parents had a child, the child would have to inherit blue eyes, because each parent only had recessive alleles to transfer genetically. If the words “Punnett Squares” rings any 7th-grade bells—this is how students are taught genetics.
While this theory is easily debunked with brown-eyed children and blue-eyed parents, the better term for why this theory is wrong is it’s “oversimplified.”
Geneticists have come a long way since 1907 when Charles and Gertrude Davenport first developed this theory of eye color. Now, it’s clear that there are a large number of genes that play a role, not just two alleles.
How to Tell If Baby’s Eyes Will Stay Blue
You might be curious to find out will my baby’s eyes stay blue forever?. The most effective way is to look at the genes associated a baby’s eye color. For this, a simple DNA test is needed.
That’s why, in the fall of this year, SneakPeek will be introducing the SneakPeek Early Traits DNA Test. It’s an easy, at-home test that just requires a quick rub of your child’s inner cheek with a cotton swab. From there, you can send the cotton swab back in a prepaid envelope and, in 2-3 weeks, learn so much about your growing baby, including what your baby’s eye color will be without having to “wait and see” if your child’s eyes will change.
This process is pain-free, and your data is privacy-protected. Best of all? The results come with many incredible insights into your child’s development. You can learn about their eventual hair color, how tall your child be, and even the pattern of their irises. Take this opportunity to learn everything you can about the amazing little wonder you brought into this world.
Loving Your Baby’s Beautiful Changing Eyes
The science behind how a baby’s eyes color change with their development is fascinating. It’s also one of the first amazing changes that your growing baby will experience. Keep your eyes on your child for every little milestone, every growth, and every grin. No matter what color their eyes wind up being, they’ll always be shining with love.
Get All The Answers with SneakPeek Early Traits DNA Test
As a parent, you know that the more information you have, the better you can love and care for your child. If you’re wondering when does baby hair texture change or what color hair will my baby have, we can answer that! The SneakPeek Early Traits DNA Test can help you plan for your child’s developing needs, including genetic predispositions for nutritional profile and even their unique sleep behavior.
For a sneak peek into your baby’s future, check back in this fall.
US National Library of Medicine. The role of the retinal pigment epithelium: topographical variation and ageing changes. https://www.ncbi.nlm.nih.gov/pubmed/11450762
US Library of Medicine. Is eye color determined by genetics? https://ghr.nlm.nih.gov/primer/traits/eyecolor
Hudson Alpha. The Genetics of Eye Color. https://hudsonalpha.org/genetics-of-eye-color/
NIH. Is eye color determined by genetics? https://ghr.nlm.nih.gov/primer/traits/eyecolor
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