Your dog’s eyes look blue for one of several reasons: genetics, age, or a medical condition. The answer depends on your dog’s breed, how old they are, and whether the blue appeared suddenly or has always been there. A puppy under 16 weeks old almost certainly has temporary blue eyes that will darken. An adult dog with naturally blue eyes likely carries specific genes for it. But if your adult dog’s eyes recently turned blue or hazy, that points to a health issue worth investigating.
Puppies Are Born With Blue Eyes
All puppies are born with their eyes closed. When they open around two weeks of age, the eyes typically appear blue or grayish-blue. This happens because the iris hasn’t yet accumulated melanin, the pigment that gives eyes their adult color. Over the following weeks, melanin gradually deposits into the iris, and the color shifts toward brown, amber, or green depending on the dog’s genetics.
Most puppies settle into their permanent eye color between 9 and 16 weeks old. By four months, the color is generally stable. So if your puppy still has blue eyes at eight weeks, don’t assume they’ll stay that way. If you’re past the four-month mark and the blue hasn’t changed, your dog likely carries genes for permanent blue eyes.
Breeds That Naturally Have Blue Eyes
Some breeds are genetically predisposed to blue eyes that last into adulthood. The most well-known example is the Siberian Husky. Researchers identified a genetic duplication near a gene called ALX4 on chromosome 18 that reduces pigment production in the eye. This mutation is specific to Huskies and operates independently of coat color, which is why even dark-coated Huskies can have striking blue eyes. A 2018 study published in collaboration with Embark Veterinary found that the same type of duplication also explains blue eyes in tri-colored Australian Shepherds.
Other breeds commonly seen with blue eyes include Weimaraners, Border Collies, Dachshunds, Cardigan Welsh Corgis, and Great Danes. In each case, the blue results from low melanin in the iris. Blue eyes don’t contain blue pigment. They appear blue for the same reason the sky does: light scatters when it passes through tissue that lacks pigment, and shorter blue wavelengths scatter most.
The Merle Gene’s Role
If your dog has a mottled or patchy coat with lighter and darker areas, they likely carry the merle gene. This is one of the most common genetic reasons for blue eyes in dogs. The merle mutation involves a repeated DNA segment inserted into a gene responsible for producing a protein called PMEL, which builds the internal scaffolding that melanin needs to form properly. When this protein is abnormal, the cell can’t deposit dark pigment (eumelanin) as effectively. The result is a diluted, patchy coat and often blue or partially blue eyes.
The intensity of the merle effect depends on the length of a specific repeating sequence in the DNA. Longer sequences produce more dramatic lightening, which is why some merle dogs have two blue eyes while others have one blue and one brown, or just a blue wedge in an otherwise brown iris. Breeds commonly carrying merle include Australian Shepherds, Shetland Sheepdogs, Collies, Catahoula Leopard Dogs, and merle-patterned Great Danes.
Piebald and White Coat Patterns
Dogs with large areas of white on their face and body may carry the piebald gene, which affects how pigment-producing cells distribute across the body during development. A variant in a gene called MITF controls this pattern. Dogs with two copies of the variant can be almost entirely white, with pigment restricted to the head or a few body spots. When pigment cells fail to reach the eyes during development, the iris stays unpigmented and appears blue. This is commonly seen in white Boxers, Bull Terriers, and Dalmatians.
Heterochromia: Two Different Eye Colors
If your dog has one blue eye and one brown eye, that’s called complete heterochromia. It occurs when melanin is deposited unevenly between the two eyes. This is hereditary in many breeds, particularly Huskies, Australian Shepherds, and dogs carrying merle or piebald genes. It’s typically harmless and purely cosmetic.
There are other forms too. Sectoral heterochromia means part of one iris is blue while the rest is pigmented, creating a split-color look. Central heterochromia produces rings of different colors around the pupil. All of these result from uneven melanin distribution and are usually present from puppyhood. If your adult dog suddenly develops a color change in one eye, that’s different from hereditary heterochromia and could signal inflammation or another medical issue.
Blue Eyes and Hearing Loss
There’s a well-documented link between blue eyes, white coats, and congenital deafness in certain breeds. In Dalmatians, 8% of dogs in the U.S. are deaf in both ears and 22% are deaf in one ear. Blue-eyed Dalmatians are significantly more likely to be deaf than brown-eyed ones. The connection isn’t that blue eyes cause deafness. Both conditions trace back to the same underlying issue: a lack of pigment-producing cells. These cells play a role not just in eye and coat color but also in the inner ear, where they help maintain the fluid environment that allows hearing to function.
Countries that exclude blue eyes from the Dalmatian breed standard have lower deafness rates, suggesting that breeding away from the trait reduces risk. If your blue-eyed dog doesn’t respond to sounds from one side or startles easily when approached from behind, a hearing test called a BAER test can determine whether they have partial or complete hearing loss.
Light Sensitivity in Blue-Eyed Dogs
Because blue eyes contain less melanin, they let more light pass through the iris. Some blue-eyed dogs show noticeable light sensitivity, squinting or blinking more in bright environments. Dogs with the merle gene can be particularly affected. This discomfort in bright light is similar to what fair-skinned, light-eyed humans experience. If your blue-eyed dog seems uneasy outdoors on sunny days, providing shaded areas and avoiding peak sun exposure can help.
When Blue Eyes Signal a Health Problem
If your dog’s eyes were brown and have recently taken on a blue or cloudy appearance, that’s not genetics. It’s a medical change that needs attention. The two most common causes are corneal edema and nuclear sclerosis, and they look different from each other.
Corneal Edema
Corneal edema is fluid buildup in the clear outer layer of the eye. It gives the eye a blue, hazy look that can appear suddenly. The cornea stays clear because two layers (one on the outside, one on the inside) actively pump fluid out. When either layer is damaged, fluid seeps in and the cornea turns cloudy blue.
The most urgent cause is glaucoma, a condition where pressure inside the eye rises to damaging levels. Left untreated, glaucoma can destroy vision permanently. Other causes include corneal ulcers (scratches or infections on the eye’s surface), uveitis (inflammation inside the eye that can cause the eye to look red and painful), and lens displacement. If the blue haze appeared over hours or days, especially if your dog is pawing at the eye, keeping it closed, or seems to be in pain, this warrants a prompt veterinary visit.
Nuclear Sclerosis
If your dog is over seven or eight years old and you’ve noticed a gradual, even bluish-gray haze in both eyes, the most likely explanation is nuclear sclerosis. This is a normal aging change. The lens of the eye produces new fibers throughout life, and over time the center of the lens gets compressed and dense. This compression scatters light, creating a pearly, bluish tinge that’s visible in normal lighting.
Nuclear sclerosis does not significantly impair vision. Dogs with it can still see well and navigate their environment normally. It’s easy to confuse with cataracts, but the two are different. A cataract is an actual opacity in the lens that blocks light. A mature cataract affects the entire lens and causes meaningful vision loss. Nuclear sclerosis, by contrast, looks hazy but still allows light through. A veterinary eye exam can distinguish between the two, which matters because cataracts may eventually need surgical treatment while nuclear sclerosis does not.
How to Tell What’s Causing Your Dog’s Blue Eyes
A few quick questions can help you narrow it down. Has your dog always had blue eyes, or is this new? If they’ve had blue eyes since puppyhood and belong to a breed known for the trait, genetics is the answer. If your dog is under four months old, the blue is likely temporary.
If the blue is new, consider your dog’s age. A senior dog with a gradual, symmetrical haze in both eyes probably has nuclear sclerosis. A dog of any age with sudden blue cloudiness in one eye, especially with squinting, redness, or discharge, could have corneal edema from glaucoma, an ulcer, or inflammation. Sudden changes in eye appearance are the ones that call for veterinary evaluation, because conditions like glaucoma can cause irreversible damage within hours to days.