Causes of Cat and Dog Eye Discoloration: Understanding

In a typical scenario, after the lacrimal glands secrete tears to moisten the eyes, these tears naturally flow through the tear ducts and into the nasal cavity, preventing any overflow from the corners of the eyes.

However, if an excessive amount of tears is produced or if the nasolacrimal ducts are blocked, the tears cannot drain properly through the ducts. This results in the tears溢出 from the inner corners of the eyes, a condition known as epiphora. The excess moisture can then stain the fur, leaving behind noticeable brown tear streaks.

These tear streaks not only detract from the facial aesthetics of cats and dogs but can also lead to serious issues, such as the proliferation of bacteria and fungi, which may cause eye infections and inflammation.

So, what are the reasons behind the formation of tear streaks in cats and dogs?

1. Entropion

Entropion, or eyelash inversion, occurs when the eyelids roll inward, causing the eyelashes to constantly irritate the cornea. This discomfort can lead to frequent pawing at the eyes and can significantly contribute to the development of severe tear streaks.

Therefore, if a cat or dog has inverted eyelashes, it's best to gently trim them with small scissors. Additionally, if the fur around the eyes is particularly long, it should be trimmed regularly to prevent tear streaks effectively.

2. Ear Infection

You might not immediately associate tear streaks with ear issues, but cats and dogs have a sensitive area where the auditory and facial nerves intersect on their faces. When the ear canal is infected with bacteria, viruses, molds, or parasites, or if there is swelling, pain, or itching, they may frequently scratch at their ears with their hind legs.

The pain from the ear infection can radiate to the eye area, stimulating the lacrimal glands to produce an excess of tears. When these tears cannot be drained through the nasolacrimal ducts, they overflow from the corners of the eyes.

3. Congenital Factors

Primary hyperplastic lacrimation is a hereditary condition where tears are excessively secreted, often leading to the formation of tear stains. Studies suggest that up to 2025% of small dogs are born with shallower tear ducts, which, combined with insufficient eyelid space, prevent tears from being retained. In cats, breeds like the Persian and Himalayan are more prone to tear stains due to their genetic makeup.

4. Diet

If a cat or dog's tear streaks are not due to congenital factors or ear disorders, the primary cause is often an excessive salt intake in their diet. Cats and dogs that consume too much salt or human food can easily suffer from heat, eye boogers, and eventually, tear stains.

Therefore, it's important to keep the diet of cats and dogs light and to control their salt intake. Excessive salt not only causes tear stains but also imposes a heavy burden on their metabolism.