When dogs have white mucus in their eyes, it is usually due to overproduction of tears or epiphora. Yellow-green mucus usually indicates conjunctivitis or sicca syndrome and red-brown mucus indicates old tears.
Here is an overview before we take a closer look at the potential causes:
Color of mucusMost common causesWhite / GrayOverproduction of tears, epiphora, corneal ulcerYellow / GreenKeratoconjunctivitis Sicca, corneal ulcer, conjunctivitisRed / BrownOld tears, epiphora
When it comes to the eyes, early action is the be-all and end-all. Because if left untreated, inflammation can often limit the dog's vision in the long term. [1]
Below you will learn about the 6 most common causes, their symptoms and what you should do in specific cases.
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#1 Overproduction of tears
Tears are essential for eye health. On the one hand, they ensure that dirt is removed and at the same time supply the cornea with oxygen.
Tears normally drain through small channels on the inside of the eye. In many breeds, however, a slimy mess forms after a certain time. It consists of:
- Dried tears
- oil and tallow
- Dust and other contaminants
- Dead cells [2]
Because the dog has its eyes closed at night, too much tear fluid is often produced. This explains the white mucus that can usually be seen on the eyes in the morning.
This is completely normal and usually nothing to worry about. However, if your dog suddenly produces large amounts of it, this could indicate problems.
Other typical eye symptoms include redness, a cloudy appearance, frequent blinking and sudden sensitivity to light. [3]
While sleeping, some dog breeds often naturally produce too much tears. In combination with dust and other contaminants, a white mucus often forms overnight on the inside of the eye. However, this is completely harmless.
#2 Conjunctivitis
The most common form of eye inflammation is infection of the conjunctiva. Doctors also refer to this as “conjunctivitis”. Typical triggers for this are:
- Allergies
- Injuries
- Clogged tear ducts
- Birth defects
- Glaucoma
- Dry eyes
- distemper [4]
This can usually be recognized by the eye becoming red. It is not for nothing that the infection is also called “red eye” in English-speaking countries.
In addition, a yellow-green mucus usually forms around the eye. This is mostly pus and dried tear fluid. Other typical symptoms are:
- Watery eyes
- Eyelids sticking together
- Constant rubbing of the eye
- Eyes begin to fester
- Dog keeps eye closed
- Frequent blinking
- Swollen eyelids [5]
If left untreated, this can lead to permanent restrictions. Therapy depends on the underlying cause. In any case, you should see a doctor here.
In dogs with conjunctivitis, the affected eye usually becomes very red. Among other things, a yellowish green mucus also forms on the eyes. It is also typical for affected dogs to blink frequently, their eyelids to swell and often stick together.
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#3 Epiphora
If too much tear fluid forms and the eye constantly leaks, then doctors speak of an “epiphora” – or, in layman’s terms, “eye discharge”.
In most cases, blocked nasolacrimal ducts or poor eyelid function are responsible. The latter occurs more frequently in the following breeds:
- cocker spaniel
- Bulldogs
- poodle
- Lhasa Apso
- Pekingese
- Shih Tzu [6]
In individual cases it is also triggered by injuries, inflammation of the nasal mucosa, allergic reactions, parasites or even congenital anomalies.
You can usually tell if the fur on the inside of the eye is constantly moist. White or brown mucus in the eyes is also typical. Other symptoms include:
- Frequent blinking
- Redness in the eye
- Unpleasant smell on the eyes
- Irritation or inflammation of the skin
- Brown spots around the eye [7]
A detailed diagnosis is essential for treatment here. In the long term, eye discharge can lead to painful inflammation in and around the eye.
Dogs with epiphora struggle with constant eye leaks. You can recognize it primarily because the fur on the inside of the eyes is constantly wet and brown spots can be seen. The increased formation of mucus can also indicate this.
#4 Old tears
Dog tear fluid also contains, among other things, a pigment called “porphyrin”. However, when exposed to air for a long time, it becomes increasingly brown-red.
This also explains, among other things, why many white dog breeds constantly have a brownish discoloration around their eyes. But this is more of a cosmetic problem. [8]
There is no reason to worry here. Not even if it forms into whole clumps of mucus. The following has proven effective in preventing discoloration:
- Wipe the dog's eyes several times a day with a cloth dipped in warm water.
- Make sure the fur around the eye is cut relatively short.
- Purchase a special eye solution from the pharmacy designed for dogs.
Within a few months, the discolored fur should grow out and the problem should disappear. This is usually unnecessary for brown and black breeds.
A visit to the doctor is only advisable if a lot of tears suddenly form, the eye is red or the dog is constantly scratching its face. [9]
If dogs' tears come into contact with the air for too long, a reddish-brownish lump of mucus usually develops. As a rule, this is harmless and is just a cosmetic problem that can be solved by regular cleaning.
#5 Keratoconjunctivitis Sicca
When the dog's immune system attacks and destroys its own tear glands, doctors also speak of “Sicca syndrome”. Typical causes of this are:
- Viral infections
- Severe poisoning
- Hormonal disorders
- Neurological problems
- Congenital disorder [10]
Due to the associated dryness, the body tries to produce more white mucus to lubricate the eyes. However, mucus cannot replace tears.
For this reason, the eyes usually become reddish and there is unusual pigmentation on the cornea of the eyes. Other typical symptoms are:
- Yellowish crusts on the eyes
- Duller looking eyes
- Visible blood vessels in the eye
- Increasing pain
- The entire eye is covered in mucus [11]
If left untreated, this disease can lead to blindness. Artificial tears are usually used in combination with medication for therapy.
In very severe cases, surgical intervention may also be necessary. However, this is usually only used as a last option because it involves increased risks.
Dogs with keratoconjunctivitis sicca usually have such dry eyes that white mucus automatically forms in the eyes. Over time, it can usually be recognized by the eyes becoming red, a yellow crust forming and blood vessels becoming visible.
#6 Corneal ulcer
The cornea of the eye is roughly comparable to the windshield of a car. It also consists of several layers – three in total.
In most cases, a corneal ulcer is caused by injuries to the back layers of the cornea. Typical causes of this are:
- Scratches from cats
- eyesore
- Cushing's syndrome
- diabetes
- Hypothyroidism
- Aggressive shampoo [12]
This leads to a dangerous accumulation of fluid in the eye, which usually causes it to become cloudy. Increased mucus and tear formation are also typical.
To make a diagnosis, the vet usually puts a special dye on the eye, which makes the ulcer visible in neon yellow. Other classic symptoms are:
- Excessive blinking
- Redness of the eyes
- Dog keeps eye closed
- Swollen eyes
- Severe pain
- Lack of tears
- Frequent rubbing of the eye [13]
The treatment depends on the level of severity. In simple cases, eye drops may be sufficient. In severe cases, surgery may also be necessary.
Dogs with a corneal ulcer usually experience increasing pain in the affected eye. Among other things, the ulcer can be recognized by the fact that the eye becomes red and cloudy and an increasing amount of white mucus forms around the eye.
Rare causes
- Glaucoma: There is a discharge from the eye here, but it is more watery and not mucous. It can also be recognized by cloudier eyes.
- Breed-specific problems: Due to their breeding, some breeds cannot close their eyes completely. A variety of eye problems are inevitable here.
- Anomalies: Congenital defects or developmental disorders of the eye can lead to too much or too little mucus forming in the eye.
- Entropion: In some breeds, the lower eyelid is partially rolled up, so that the eyelashes cause constant irritation to the cornea on the eye.
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