When Do Babies’ Eyes Change Color?

The answer to that question is more nuanced than you might expect. Let’s delve into the world of eye color and explore when and why it may change.

Contrary to popular belief, not all babies are born with blue eyes. Many are, but some are also born with gray eyes, which may verge on gray-brown.

Eye color (both at birth and later on) is dependent on genetics, which also determine hair and skin color.

A lot of children’s eyes change color, regardless of what shade they start out with. Often, that shift is less dramatic than, for instance, a change from blue to brown (e.g., a lighter shade of brown may become darker, etc.).

When do babies’ eyes generally change?

Your baby’s eyes may change at any point during his first few months of life, but it often happens by 6–9 months. 1 If your baby’s eyes do change color, it’ll be from light to dark. Your baby’s brown eyes won’t turn blue, but blue may shift to green or brown over time. 2

Two factors determine eye color:

• The amount of melanin in the iris
• The genes that influence its production

How melanin affects eye color

Melanin is the pigment that determines your eye, skin, and hair color. It’s produced in the structure of the eye called the iris, the colored part of the eye that surrounds the pupil (and controls the amount of light that enters the eye by adjusting the size of the pupil).

Because melanin absorbs light, eyes with more of it appear darker (e.g., brown). Conversely, lower amounts of melanin give rise to lighter-colored eyes. When there’s less melanin, collagen fibers in the iris scatter light, causing eyes to appear blue or green. 3 1

You might expect each eye color to have a separate pigment, but all eye colors depend on the amount of melanin in the iris.

How genetics affect eye color

How much melanin the iris produces depends on the genes parents pass on. Scientists previously thought that just one gene controlled eye color, but now they believe that several play a role.

Two genes, called OCA2 and HERC2, hold the most influence: 3

• OCA2: This controls the production of the P protein, which influences the cellular structures that produce melanin (known as melanosomes). Since more melanin leads to darker pigmentation, variations in this gene have a major effect on eye color.
• HERC2: This contains a region that controls the expression of OCA2. This means a variation in HERC2 can “turn off” the OCA2 gene, reducing melanin production and creating lighter eyes.

Why do children’s eyes change color?

While our understanding of the genetics behind eye color has come a long way, there’s still not a definitive answer for why some children’s eyes darken over time.

On a cellular level, an increase in melanin production changes your baby’s eye color. What isn’t clear is what genetic or environmental factors cause this.

Maybe you remember doing Punnett squares back in high school biology class, filling in the combinations of dominant brown-eyed and recessive blue-eyed genes.

Now that we know more about the genetics of eye color, that method isn’t a guarantee for predicting what your baby’s eye color will be.

Generally speaking, children’s eye colors match those of their parents when both parents have the same eye color. If both parents have blue eyes, the baby probably will, too. If your blue eyes turned brown, that’s a strong indicator that it could happen to your baby as well. 4

But your baby’s eye color isn’t just determined by your genetics, but also the genetics of your own parents. Some genes can skip generations, resulting in a baby with your mother’s eyes. 5

Ultimately, it’s hard or impossible to know for sure what color your baby’s eyes will be. This is just one of the many surprises you get to look forward to when you become a parent.

Which eye color is the least common?

It’s tricky to say which eye color is the least common, as it depends on how exactly you define different eye colors. For example, some surveys may consider hazel and brown to be the same, or may not offer gray as an option.

A survey by the American Academy of Ophthalmology found that brown and blue were the most common eye colors in the US, while green was less common. 6

Most newborn changes in eye color are normal, but there are a few instances where you should consult with your pediatrician:

• Changes in the whites of the eyes: As you know, it’s normal for babies’ irises to change color. However, watch out for any redness in the whites of the eyes, which can be a sign of an infection (e.g., conjunctivitis, commonly known as pink eye).
• Differently colored eyes: Some babies are born with two different eye colors, a condition that’s known as heterochromia. Often, it’s nothing to worry about, and is the result of a harmless genetic mutation. However, heterochromia can also be a symptom of a medical issue, such as Horner’s syndrome, a condition that stems from nerve damage. Pay a visit to your pediatrician to rule out any medical problems. 7

Despite the progress science has made in understanding eye color, you still can’t predict exactly what your little one’s will look like. Again, consider this one of your baby’s first big surprises for you!

You might want to take extra photos to document your baby’s initial eye color—if his eyes change, he might not believe he used to look any different.