Blue is a somewhat rare yet striking eye color, making it a memorable facial feature. From light blue eyes to shades of blue-gray, these eyes don't actually contain blue pigment. Rather, they appear blue because they don't have as much of the brown pigment present in dark-colored eyes.

Keep reading as we discuss what determines blue eye color, whether you can change your eye color and the benefits and risks that people with light-colored eyes may have.

Where do blue eyes come from?

Eye color, in general, is determined by your genetics and a substance in your body called melanin.

Melanin

This is the pigment that provides color to your eyes, skin and hair. People with more melanin usually have darker features. Those with less melanin have lighter features.

Eye color is created by the amount, distribution and type of melanin present in the iris, or the colored area of your eye. The iris consists of two layers: the stroma (front layer) and the pigment epithelium (back layer). The levels of melanin in each of these layers are what gives your eyes their color.

Most eyes have brown pigment in the back layer of the iris. Those with brown eyes typically have a lot of melanin in both layers, while those with light eyes have little to no melanin in the front layer. If your eyes are blue, there's no pigment in the front layer. [1]

Blue eyes hold no blue pigment at all — they look blue for the same reason the sky does. The stroma scatters the light that enters it, so the shorter, blue wavelengths bounce back to you while the longer ones are absorbed. Scientists call this Rayleigh scattering, or the Tyndall effect.

What makes eyes light blue?

The shade comes down to how little pigment sits in that front layer. With almost none, more light scatters back and the iris looks pale, light blue. A bit more pigment gives a deeper, richer blue. A little more still, and you get the soft blue-gray some people call steel or slate. Light blue eyes and deep blue eyes have the same cause — a low-pigment front layer. The difference is just a matter of degree.

Genetics

Genetics play a role in determining your eye color. In the past, scientists believed that one gene controlled the color of eyes you inherited and that you could only have blue-colored eyes if both of your parents had blue eyes. However, they now know that multiple genes are involved in eye color inheritance and that parents can have children with eye colors different than their own. [1]

Are blue eyes a mutation?

A genetic mutation is believed to be the cause of blue eyes. A genetic mutation is a change in DNA sequence that occurs during DNA replication when cells divide. The blue eye genetic mutation is associated with a reduced amount of pigment (melanin) in your irises, causing your eyes to appear blue. [2] Researchers at the University of Copenhagen traced it to the HERC2 gene, which turns down a neighboring gene that helps make melanin. [2]

How many people have blue eyes?

So how rare are blue eyes? Worldwide, fairly rare. Blue is the second most common eye color after brown. It occurs in 8% to 10% of the global population. [3]

Many people in Northern Europe have blue eyes, and they're especially common in Finland, Estonia, Iceland and Sweden. In the United States, around 27% of the population has blue eyes. [4]

Are all blue-eyed people related?

If you share the same blue eye color with someone else, it could be that you're (very) distantly related. Research suggests that you may share a common ancestor who had the same blue-eye genetic mutation. It's believed that 6,000 to 10,000 years have passed since this genetic mutation first occurred. [2]

Can you change your eye color?

Wearing colored contact lenses is the most common and safest way to change or enhance the appearance of your eye color. There are surgical procedures that alter the iris, but they may not be safe and generally aren't recommended.

You don't need a vision problem to wear color contacts. They come in prescription and plano (non-corrective) versions, so you can change your look even if your sight is perfect. A daily lens like DAILIES Colors gives you a fresh, natural shade each morning, with no cleaning or cases. AIR OPTIX Colors is a monthly option that uses SMARTSHIELD technology to resist deposits. Either way, color contacts are still medical devices, so you need a valid prescription and a proper fitting — ask your eye doctor first. When you're ready, browse the full range of color and enhancing contact lenses, with free shipping and insurance or FSA/HSA benefits included.

Benefits of having blue eyes

There may be one upside to having light eyes. People with blue eyes may be less likely to develop seasonal affective disorder (SAD) than those with brown eyes. SAD is a form of depression that occurs at certain times of the year, often in winter when daylight hours are shorter. [5] Further research is needed to confirm the connection between eye color and the risk of SAD.

Limitations and risks

The flip side of low pigment is a little less built-in shade from bright light.

Sun protection

Melanin absorbs UV light, and light-colored eyes carry less of it, so more light reaches the eye. That's a good reason to be diligent about sun protection. Wear sunglasses with 100% protection against UVA and UVB rays whenever you're outdoors, no matter what color your eyes are.

Whatever color your eyes are, keep up with regular eye exams too. Your eye doctor can check your eyes and update your prescription when you need it.

Sources

[1] Cleveland Clinic — eye color depends on how much melanin is in the iris; with little or no melanin in the front layer, eyes look blue or gray, and many genes affect eye color. my.clevelandclinic.org

[2] University of Copenhagen (Eiberg, 2008) — all blue-eyed people share one common ancestor; the mutation, in the HERC2 gene, lowers melanin in the iris and arose an estimated 6,000 to 10,000 years ago. sciencedaily.com

[3] Medical News Today — blue is the second most common eye color, and an estimated 8% to 10% of people have blue eyes. medicalnewstoday.com

[4] American Academy of Ophthalmology — a 2014 Harris Poll found 27% of Americans have blue eyes. aao.org

[5] University of South Wales (Workman) — in a study of 175 students, people with light or blue eyes scored lower on a seasonal-pattern (SAD) assessment than those with darker eyes.