When do babies' eyes change color?

Your baby's eye color may change over the first few months to a year. Newborns sometimes have dark blue or slate-gray eyes that gradually turn blue, green, hazel, or brown. A few children's eyes will continue to change color until adulthood.

Eye color is determined by the amount of melanin in the iris – the colored part – of the eye. Melanin is a protein that pigments, or colors, your eyes as well as your skin.  

The iris is divided into two layers. Almost everyone, including people with blue eyes, has melanin in the back layer. The amount of melanin in the front layer varies, defining a baby's eye color.

Brown eyes contain a lot of melanin, while green and hazel eyes contain a bit less. And blue eyes contain very little melanin in the front layer of the iris. That results in more blue light reflecting from the iris, making eyes appear blue.

Some babies are born with their final eye color, but others experience changes as melanocytes – specialized cells that create melanin – ramp up production.

What determines newborn eye color?

Your baby's eye color is determined by a complex set of many genes. These genes determine how much melanin is produced, transported, and stored in their eyes.

The genes that are responsible for brown eye color are dominant over those that result in blue eye color. A baby who has a parent or a grandparent with blue eyes may inherit that color, with the odds increasing with every close relative who has blue eyes. People of Asian or African descent are very likely to have brown eye genes, while babies of other races may have genes that result in other eye colors.

High levels of melanin in the eyes and skin help protect against the sun's powerful rays – which is why brown eyes are more common in sunny parts of the world and less common in less sunny northern climates.

When do babies' eyes change color?

Baby eye color usually changes in the first three to six months of life, although some children can have significant changes up until their first birthday.

In a few children, eye color changes can continue for years. Most children have a stable eye color by the age of 6 years old. That said, some research suggests that 10 to 15 percent of white children continue to see changes in their eye color into adolescence and even adulthood, due to changes in the amount and distribution of melanin in the iris.

Are all babies born with blue eyes?

It's a myth that all babies are born with blue or gray eyes. While some babies are indeed born with blue or gray eyes that stay that color or gradually change, others are born with brown, green or hazel eyes.

In fact, most babies are born with brown eyes that stay brown. A study of 192 children born in California found that nearly two-thirds were born with brown eyes, while roughly 21 percent were born with blue eyes. Another 6 percent had hazel eyes, 10 percent had "indeterminate" eyes, and less than 1 percent had mixed eye color.

Interestingly, every human on earth had brown eyes until about 10,000 years ago. Scientists think a mutation in a gene that controls melanin production led to a single common ancestor with light-colored irises.

What color eyes will my baby have?

In the months after birth, a child's irises may gain more pigment and become more green, hazel, or brown in color. However, brown eyes won't get "lighter" or bluer. While most babies have their final eye color by the time they're 1 year old, some see changes until adulthood.

There's no surefire way to predict your baby's adult eye color. A parent's eye color hints at a baby's final eye color, but it's not conclusive. That said, your eyes can give you a general sense of your baby's odds for various eye colors:

• Two blue-eyed parents will very likely – but not always – have a blue-eyed child
• Two brown-eyed parents are likely to have a brown-eyed child
• The odds are about even for having blue or brown eyes if each parent has one eye color
• If a grandparent has blue eyes, a baby's chances of having blue eyes increases

According to national surveys, in the U.S. green eyes are the rarest eye color, followed by hazel and blue. Brown is the most common eye color worldwide.

It's also possible to have one eye color near the pupil and another near the edge. (That's due to variations in the amount of melanin in different parts of the iris.) However, if your baby has one brown eye and one blue eye, tell their doctor. This often signals a rare genetic condition called Waardenburg syndrome.