Cat Eye Discharge: Symptoms, Causes & Diagnosis

Unfortunately, eye issues are extremely common in cats. Those big cute eyes we all love so much can quickly become squinty, inflamed or full of discharge.

It can be difficult to know what is a major concern and what isn’t. Some cats are simply more prone to “eye boogers” while other cats may have an injury or infection.

Eye issues can very quickly become serious, so don’t delay seeing the veterinarian if this is something new for your cat.

cat with big eyes

Normal Eye Discharge In Cats

Feline ocular discharge should be minimal and clear and appear dusty and brown when dried for it to be called normal. Felines groom themselves but their eye corners may need a little help from time to time – like 1 to 2 days.

This depends on the breed since there are felines that are more prone to releasing tears due to their short faces. Use cotton balls and saline solution for cleaning the sleep off.

Brachycephalic kitty breeds like Persians and their cousins like the British Longhair and Shorthair, Chinchilla, Exotic Shorthair, and the Himalayan have short heads and may need everyday eye gunk cleaning.

Eye Discharge Problem

The good thing about regularly helping your cat clean its eyes is that you get to check what normal eye discharge is. There are days, however, when your cat’s eye boogers are more than normal and this is when you need to check for ocular discharge consistency and redness.

Is the consistency or thickness of your cat’s ocular discharge clear and watery? Is it a combination of clear and mucus? Or is it thick and mucousy green or yellow?

Causes and Symptoms Of Feline Eye Discharge

By far the most common cause of eye discharge in cats is contagious diseases. These are especially common in kittens that haven’t had any vaccines yet. Cats with compromised immune systems such as those with feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are also prone to these types of infections.

Kittens with eye discharge will also usually have some upper respiratory symptoms as well. They might sneeze or have a runny nose. In most cases, these sorts of infections are normal for kittens and do not cause any problems.

However, this can’t true for all kittens. Some kittens will have difficulty fighting off eye and upper respiratory infections. These infections can quickly become serious, with accompanying life-long issues.

If your otherwise healthy adult cat is fully vaccinated and never goes outside, it is more likely that another issue is causing the eye discharge. Injury to the eye, allergies or even its breed. 

Black “eye boogers” or tear staining may be normal for your cat, especially purebreds. However, excessive amounts may still need medical attention such as the use of eye drops.

  • Feline Herpesvirus

Feline Herpesvirus is unfortunately very common in cats and affects the eyes and upper respiratory tract. The standard “feline distemper” vaccine includes vaccination for this disease. However, many young kittens catch it before they have a chance to be vaccinated.

Symptoms of a feline herpesvirus infection include painful and squinting eyes, clear or white eye discharge, and nasal congestion which is often accompanied by sneezing. Typically, there is more respiratory discharge than discharge from the eyes, but its not always the case.

Serious infections can cause permanent damage to the eyes. These include, but not limited to, non-healing ulcers and permanent fusion of portions of the eyelids to the cornea.

Most healthy cats can fight off symptoms on their own. However, without antiviral treatment, the virus will remain dormant in the body for life. When your cat goes through periods of stress, the herpes virus can flare up.

Usually, this will be seen as inflammation and squinting in one eye. For this reason, it may be recommended to begin antivirals at the first signs of feline herpes infection.

Also, avoid getting your kitty into stressful situations like a sudden change in environment, loud noises, and visitors as these will cause recurring sickness.

  • Feline Calicivirus

This virus has extremely similar symptoms to feline herpesvirus. Like the latter, it can also be prevented by the “feline distemper” vaccine. But unlike feline herpesvirus, calicivirus can cause ulcers in the mouth.

Calicivirus can sometimes become serious, especially if the mouth ulcers are making your cat reluctant to eat. There is no cure; only supportive care can be offered. This includes pain and fever management, antibiotics for secondary infections, syringe feeding, etc.

  • Feline Chlamydia

This bacteria affects the eyes and upper respiratory tract like so many other common cat diseases. Unlike herpesvirus and calicivirus, it mainly causes symptoms in the eyes. Sneezing and nasal discharge are also less severe.

Swollen, pink, painful eyes with yellow or green discharge are signs of chlamydia in cats. There is a vaccine for this disease but it is not included in all feline distemper vaccines. Luckily, feline chlamydia can be effectively treated with antibiotics.

As mentioned, feline chlamydia is a common cause of eye discharge in cats but is often underdiagnosed in favor of the even more common herpesvirus.

If your kitten has eye discharge that appears to be from an infection but does not have significant nasal discharge or sneezing, chlamydia is highly probable. This is important for your veterinarian to consider because chlamydia usually needs specific antibiotics to treat it, not just a broad spectrum.

  • Mycoplasma

Mycoplasma is yet another bacteria that attack the cat’s eyes. Mycoplasma is not typically a primary infection but often occurs when the eyes are already infected with one of the above diseases.

Mycoplasma will cause yellow to green discharge and can also cause very serious ulcers in the eyes. Antibiotics in the form of eye ointment or pills may be prescribed. Unfortunately, there is no vaccine for this condition.

  • Injury or Ulcers

The cornea is the clear surface on the front of the eye that protects it. Scratches or ulcers in the cornea can cause inflammation of the eye and may cause discharge. Without infection, the discharge should be clear.

If an ulcer or injury to the eye is serious enough, treatment will still be needed to prevent infection and heal properly. The cornea will scar when damaged, so your cat may experience some vision loss.

  • Feline Infectious Peritonitis

A far less common but serious cause of eye discharge is FIP. This disease is the result of coronavirus infection.

Cats are commonly exposed to this virus, but only rarely will it result in FIP. Once the clinical signs of FIP occur, it is nearly 100% fatal within a few weeks.

The symptoms of this disease are vague and vary in every cat. When cats are initially exposed to coronavirus, they may have some eye and nose discharge. Once the signs of eye discharge and congestion go away, the virus may have already been fought off or it may lay dormant for weeks to years before FIP occurs. 

Again, FIP or coronavirus is an unlikely cause of eye discharge, but it is something to keep in mind.

  • Allergies

Just like people, cats can have allergies that can make their eyes water and run. This discharge should be clear but may dry black. If allergies are the cause, your cat will likely have slightly “puffy” eyes or maybe itchy and eye gunk is clear and watery.

Epiphora or excessive clear ocular discharge often has something to do with your kitty’s tear ducts; they may be blocked or irritated.

If your kitty is suffering from excessive discharge in only one eye, it could mean a foreign body. But if both eyes are blocked, then, it could be an allergic reaction.

Substances like pollen, mold, mildew, and dust are common allergy-inducing particles. Chemicals like cleaning products, flea control products, perfumes, and cigarette smoke can also cause your kitty eye irritation.

Typically, no treatment is required for mild seasonal allergies. However, if your cat seems to be uncomfortable, there are many treatment options your veterinarian can recommend.

Excessive clear and watery eye discharge may be flushed out with a saline solution. In addition, have your kitty away from irritants, as well as store all chemical substances around the house properly to avoid toxic fumes from reaching your cat.

Veterinarians may also provide your cat with steroids to reduce the effects of allergic reactions. Continued long term irritation to the eyes can cause issues, so be sure to address allergies if they are year-round.

  • Blocked Tear Duct

Certain breeds of cats are prone to get blocked tear ducts. This will cause tear staining and “eye booger” buildup. Normal eye discharge will accumulate where you can see it; often turning the brown or black.

Ducts can be fully or partially blocked. Inflammation can also cause blocked tear ducts.

In mild cases, it is likely that nothing needs to be done for your cat. However, more serious cases may affect tear production and cause chronic dry eyes for your cat.

Your veterinarian can best determine if the issue is a blocked tear duct and if your cat needs medical treatment.

  • Conjunctivitis

Does your kitty have red or inflamed eyes along with excessive clear and watery ocular discharge? If it does, your kitty may have conjunctivitis, also known as pink eye – one of the most common eye problems for felines.

Most cats will have it at least once in a lifetime, especially at a young age when their immune system is not yet as well developed.

Regular conjunctivitis may clear up without any treatment. But just to make sure, maintain the regular eye cleaning using saline solution.

In addition, avoid using over-the-counter eye drops unless you have already visited the vet and they have been recommended.

  • Bacterial Infections

There are cases when your kitty’s conjunctivitis advances and its ocular discharge becomes greenish or yellowish. When these happen, it may possibly be due to bacterial infection.

One thing you may need to check is if your kitty, rather than having excessive tearing, is experiencing the opposite – Keratoconjunctivitis Sicca (KCS) or dry eyes. Dry eye problem is not a common occurrence among cats but it is said to be related to long-term herpes virus infections.

Cats suffering from dry eyes have tear glands that produce fewer secretions than what is required to keep the eyes moist. Because of this, their eyes are prone to irritation and redness; and rather than clear liquid, their eyes tend to have inflamed or damaged cornea and mucus ocular discharge. If left untreated, a poor cat with this eye problem can go blind.

Bacterial infections in your cat’s eyes must be checked first by the vet before being treated. This is to properly identify which bacteria are affecting the feline’s eyes, as well as to see any underlying illnesses and other medical complications.

Moreover, your vet will give you the proper prescription and dosage – any over-the-counter drug you apply on your cat may be risky and could be toxic.

Dry eyes in felines can be treated using artificial tear solutions, ointments, and steroid medications for kitties that still have intact cornea. More serious cases for felines may require surgery.

cat with watery eyes


Your veterinarian has several diagnostic tools to determine the cause of your cat’s eye discharge. The most basic tool is the ophthalmoscope.

Nearly identical to what human eye-doctors use, the veterinarian will shine a bright light to examine both the inside and the outside of the eye. This is called an ophthalmic exam.

If your veterinarian suspects that a contagious disease is the cause of your cat’s eye issues, they may want to send out a sample. The eye will be swabbed and sent to a laboratory to determine the exact bacteria or virus that’s causing the infection. This way the veterinarian will know which medications to use for treatment.

Another common procedure is staining the cornea. This will help your veterinarian to see if there are any scratches or ulcers in the eye.

There are many additional diagnostic tools that can be used on the eyes. The eye pressure can be checked, the tear production can be measured, and the tears can also be checked if they are draining correctly.

infected eye of a cat

Other Things to Take Note of For Excessive Ocular Discharge

Cloudy Eyes – if your cat squints and rubs its head more often, your cat may have Uveitis. This is an inflammation of the internal structure of the eyes.

This is sometimes indicated by eye ulcers which are caused by a scratched eye, chemicals, secondary infection or head injuries. If left untreated, this could lead to blindness.

Pain – if your feline friend experiences pain along with excessive eye boogers, this could mean inner eye and cornea problems. Tearing may be accompanied by frequent pawing at its eye, as well as sensitivity to light.

You will have to consult with the vet to properly identify which part of its eye is being affected and to get the corresponding treatment.

Diarrhea and Fever – A cat with conjunctivitis, along with a fever untreatable by any antibiotic, diarrhea, and labored breathing may be suffering from Peritonitis, which, as mentioned, is a rare but fatal disease among felines – whether wild or domesticated.

If you see these symptoms or are having suspicions about your cat having these, you need to go to the vet right away.

Eyelid Problems – Sometimes, the cause of excess discharge in our kitty’s eyes may have something to do with the eyelids. Entropion, for example, happens, when the eyelashes rub against the cornea because the eyelids got folded inwards.

Trichiasis, on the other hand, is when eyelashes grow from the eyelid in such a way that they rub against the cornea.

In both cases, the cornea gets affected and the poor kitty suffers pain and eye irritation which could lead to eye ulcers, inflammation, and infection. Treatment for this will have to be done by the vet since it requires proper eyelash removal and the right ointments and other medications.

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