A cat squinting both eyes is almost always a sign of pain or irritation. Cats instinctively narrow their eyelids when something is bothering their eyes, a reflex called blepharospasm. Because both eyes are affected at the same time, the cause is usually something systemic like an infection, inflammation, or an environmental irritant rather than a simple scratch or injury to one eye.
Upper Respiratory Infections Are the Most Common Cause
The single most likely reason your cat is squinting both eyes is a viral upper respiratory infection. Feline herpesvirus 1 (FHV-1) is the leading culprit. After an incubation period of 2 to 6 days, it causes conjunctivitis that is usually bilateral, meaning it hits both eyes. You’ll typically see red, swollen conjunctiva, watery or mucus-like discharge, and squinting. Sneezing, nasal congestion, and reduced appetite often come along with it.
The acute phase of herpesvirus can be self-limiting, resolving within 10 to 20 days, but it can also progress to more serious eye problems including corneal ulcers and thick, pus-like discharge. The virus never fully leaves your cat’s body. It goes dormant and can reactivate during periods of stress, illness, or immune suppression, causing another round of squinting and eye irritation that may affect one or both eyes.
Other infectious agents that cause bilateral eye symptoms include Chlamydophila felis and Mycoplasma. Chlamydophila infections tend to cause significant swelling of the tissue around the eye along with redness and watery discharge. Calicivirus, another common respiratory pathogen, can also contribute to eye irritation alongside mouth ulcers and joint pain.
Conjunctivitis: What It Looks Like
Conjunctivitis simply means inflammation of the pink tissue lining the eyelids and covering the white of the eye. It’s the most common eye condition in cats and the most frequent explanation for bilateral squinting. The eyes look red and puffy, and there’s usually some discharge ranging from clear and watery in early or mild cases to thick and yellow-green when bacteria are involved.
Treatment typically involves antibiotic eye drops or ointment applied three to four times a day for two to three weeks, after which the discharge and squinting should resolve. Even when the underlying cause is viral (antibiotics don’t kill viruses), vets often prescribe them to prevent secondary bacterial infections that pile on while the immune system is busy fighting the virus. If your cat’s squinting doesn’t improve within a few days of starting treatment, or if the discharge gets worse, a recheck is warranted.
Corneal Ulcers and FHV-1
Corneal ulcers are open sores on the clear surface of the eye, and they hurt. Cats with ulcers squint hard, tear excessively, and often paw at their face. The most important cause of corneal ulceration in cats is herpesvirus infection. One study from the Journal of Feline Medicine and Surgery went so far as to recommend assuming an FHV-1 cause “until proven otherwise” when a cat presents with an ulcerated cornea.
While corneal ulcers from trauma tend to affect only one eye, herpesvirus reactivation can produce ulcers in both eyes simultaneously. Other possible causes include eyelid abnormalities like entropion (where the lid rolls inward), abnormal eyelash growth, and tear film problems. Corneal ulcers need veterinary treatment. Left alone, they can deepen, become infected, and in severe cases lead to a ruptured eye.
Uveitis: Inflammation Inside the Eye
Uveitis is inflammation of the structures inside the eye, and it’s a more serious possibility when both eyes are affected. It causes pain (which shows up as squinting and tearing), constricted pupils, redness, cloudiness, and sometimes a visible change in iris color. You might notice your cat’s eyes look hazy or that the pupils seem unusually small, even in dim light.
What makes uveitis concerning is that in cats it’s frequently linked to systemic diseases. Infections like feline infectious peritonitis (FIP), feline leukemia, feline immunodeficiency virus, and toxoplasmosis can all trigger it. Because of this, a vet diagnosing uveitis will often recommend bloodwork and other testing to look for an underlying cause beyond the eyes themselves. If the inflammation goes untreated, it can lead to secondary glaucoma, cataracts, or permanent vision loss.
Glaucoma: Pressure Building Up
Glaucoma occurs when fluid pressure inside the eye rises to damaging levels. Normal eye pressure in cats averages around 12 mmHg. Readings of 25 mmHg or higher, or a difference of 12 mmHg or more between the two eyes, raise red flags. In cats, glaucoma most often develops as a complication of uveitis rather than on its own, which means bilateral squinting from uveitis can eventually become bilateral glaucoma if the inflammation isn’t controlled.
Signs include a painful, squinting eye that may appear enlarged or cloudy, a dilated pupil that doesn’t respond to light, and visible redness. Cats with glaucoma may become withdrawn, lose interest in play, or bump into objects as their vision deteriorates. This is a condition where early treatment makes a real difference in preserving sight.
Environmental Irritants
Sometimes the explanation is simpler. Smoke, dust, strong cleaning products, perfumes, air fresheners, and other airborne irritants can make both eyes water and squint. If the squinting started after you changed a household product, lit a candle, or did dusty work around the house, that’s worth noting.
That said, true allergic eye disease is less common in cats than most owners assume. Conjunctivitis in cats is usually caused by infections rather than allergies. If removing the suspected irritant resolves the squinting within a day, an irritant was likely the cause. If it persists, an infection or other condition is more probable. Using an air purifier and keeping your home smoke-free can help reduce flare-ups of eye irritation in sensitive cats.
What You Can Safely Do at Home
If your cat’s squinting is mild, with no heavy discharge, cloudiness, or obvious distress, you can gently clean around the eyes with a cotton ball dampened with clean water. Wipe from the inner corner outward, use a fresh cotton ball for each eye, and dry with a soft tissue. Don’t touch the eyeball itself.
Avoid using human eye drops, contact lens solution, or any medicated product not prescribed by a vet. Many human eye medications contain ingredients that are harmful to cats, and using the wrong drop on an ulcerated cornea can make things dramatically worse.
Signs That Need Prompt Veterinary Attention
Some patterns of squinting signal something urgent. Watch for sudden cloudiness or a blue-white haze over the eye, thick yellow or green discharge, a visible third eyelid (the pinkish membrane creeping across from the inner corner), pupils that are different sizes, or any swelling that came on quickly. Behavioral changes matter too. A cat that’s rubbing its face against furniture, shaking its head repeatedly, or suddenly bumping into things is telling you something is seriously wrong.
Squinting that lasts more than 24 hours, gets progressively worse, or comes with sneezing and nasal discharge points to an infection that’s unlikely to clear on its own. The sooner treatment starts, the lower the risk of complications like corneal scarring or chronic inflammation that flares up for the rest of your cat’s life.