Most of the time, a dog’s wink is a harmless social signal or a minor reflexive response to something irritating the eye. Dogs don’t wink with the same deliberate intent humans do, but they do use eye movements as part of their body language, and they can pick up blinking habits from living closely with people. That said, frequent or persistent winking in one eye can sometimes point to a physical problem worth paying attention to.
Winking as Body Language
Dogs communicate heavily through eye contact. A direct, unbroken stare is a threat signal between dogs, so they’ve developed a whole vocabulary of ways to soften or break that gaze. Averting the eyes, blinking slowly, and briefly closing one eye are all ways a dog signals that it’s not looking for conflict. When your dog winks at you during a calm moment, it’s often a submissive or appeasing gesture, the canine equivalent of saying “we’re good.”
Some dogs also learn to wink through simple reinforcement. You notice the wink, you laugh or talk to them in a happy voice, and they file that away. Over time, they repeat the behavior because it got a positive reaction. This kind of learned mimicry is especially common in dogs that spend a lot of one-on-one time with their owners and are highly attuned to facial expressions.
The Third Eyelid Factor
Dogs have a structure most people never notice until it catches them off guard: a third eyelid, called the nictitating membrane. It sits tucked under the lower lid and sweeps horizontally across the eye rather than up and down like the outer eyelids. Its job is to clear debris, distribute tears, and protect the eye’s surface. A tear gland behind it produces roughly half the moisture that keeps the eye lubricated.
Unlike in some other animals, the third eyelid isn’t part of a dog’s normal blink reflex. But it can become visible when a dog is relaxed, sleepy, or when something pushes on the eye area. If you occasionally see a whitish membrane flash across your dog’s eye, that’s what you’re looking at. It can look a lot like a slow, exaggerated wink, and it’s perfectly normal in most cases.
When a Wink Is Actually Squinting
The important distinction is between an occasional, relaxed wink and repeated squinting or holding one eye partially closed. Involuntary squinting is a protective reflex. The eyelid contracts to shield the eye from further damage, whether that’s a speck of dust, a scratch on the cornea, or inflammation underneath. If the winking is happening frequently, only affects one eye, or your dog seems to be keeping that eye narrower than usual throughout the day, it’s more likely a physical issue than a social one.
Common environmental triggers include dust, pollen, mold spores, and household allergens. Dogs predisposed to skin allergies are also more likely to develop allergic reactions affecting the eyes, leading to redness, watery discharge, and squinting. Flushing the eye with sterile saline eye wash (available over the counter) can help clear out surface irritants. Do not use contact lens solution, which contains enzymes that can damage the eye’s surface, according to the American College of Veterinary Ophthalmologists.
Breeds That Are More Prone to Eye Issues
Certain breeds are structurally predisposed to eye problems that can look like chronic winking. Flat-faced (brachycephalic) breeds like Pugs, French Bulldogs, Shih Tzus, and Boston Terriers have prominent eyes with oversized eyelid openings. Many of these dogs can’t fully close their lids when they blink, which leaves the cornea chronically exposed to air, debris, and drying. This incomplete blink leads to irritation, and the dog compensates by squinting or holding one eye partially shut.
These breeds also tend to have reduced corneal sensitivity compared to longer-snouted dogs, meaning they may not show obvious signs of pain even when damage is accumulating. Hairs from skin folds near the nose can chronically rub against the eye surface without the dog reacting dramatically, but the irritation still drives subtle squinting behavior.
Breeds with heavy facial skin, like Shar-Peis, Chow Chows, Neapolitan Mastiffs, Saint Bernards, and English Bulldogs, face a different but related problem: eyelids that roll inward (entropion) or sag outward (ectropion). Research from the Royal Veterinary College found that in a single study year, 15.5% of Shar-Peis and roughly 9.5% of Chow Chows and Neapolitan Mastiffs were diagnosed with these eyelid disorders. When the eyelid rolls inward, the outer hairs scrape against the eyeball with every blink. That’s as painful as it sounds, and the dog’s natural response is to hold the eye partially closed.
Signs That Need Veterinary Attention
An occasional wink with a relaxed body, soft ears, and a wagging tail is almost certainly behavioral. But certain combinations of symptoms suggest something more serious is going on:
- Redness in the white of the eye paired with squinting often indicates inflammation or a corneal ulcer. Dogs with corneal ulcers typically have a noticeably red eye and thick discharge.
- Cloudiness or a bluish haze over the eye surface can signal a scratch or ulcer on the cornea.
- Thick or colored discharge, especially yellow or green, suggests infection or significant irritation beyond simple tearing.
- Pawing at the eye or rubbing the face against furniture and carpet indicates the dog is trying to relieve discomfort.
- Squinting that lasts more than a few hours or affects only one eye consistently points to a localized problem rather than a behavioral quirk.
Corneal ulcers in particular can worsen quickly. What starts as mild squinting can progress to significant pain and vision loss if the surface defect deepens. Veterinarians diagnose them by applying a fluorescent dye to the eye that highlights any damage on the corneal surface. If your dog’s “wink” is accompanied by redness or discharge, getting it checked promptly protects both comfort and long-term vision.
How to Tell the Difference at Home
Pay attention to context and consistency. A behavioral wink tends to happen during interaction with you: when you’re talking to your dog, when they’re relaxed on the couch, or when they’re playfully engaging. It alternates between eyes or doesn’t follow a pattern, and your dog’s eye looks completely normal the rest of the time, with no redness, swelling, or discharge.
A medical squint tends to persist. You’ll notice it when the dog isn’t interacting with anyone, when they first wake up, or when they’re outside in bright light or wind. It usually affects the same eye repeatedly. If you gently examine the eye and see any redness, swelling along the lid margin, visible third eyelid, or excessive tearing, that’s the eye telling you something specific is wrong. A quick saline rinse can address a stray piece of dust, but anything that persists beyond a day or comes with other symptoms is worth a professional look.