Shun Nagai“Tear stains” around a dog’s eyes are a common concern. These reddish-brown marks are not just a cosmetic issue—they can also be a sign of a dog’s health status and living environment. Tear staining can result from a wide range of factors, including genetics, environmental triggers, and daily habits, but in this article, we will focus specifically on diet.
In this article, we will clearly explain the mechanism behind tear staining and explore how diet may affect it. We will also introduce specific ingredients to avoid, as well as ingredients that may help reduce tear staining, for both dog food developers and pet owners.
What Are Tear Stains?
Tear stains are the reddish-brown or brown discoloration that appears beneath a dog’s eyes. They are mainly caused by tears running from the eyes down the face, and they tend to be especially noticeable in dogs with white or light-colored coats.
This discoloration is caused by an organic compound in tears called porphyrin. Porphyrin is a byproduct formed when red blood cells break down. Because it contains iron, the tear residue oxidizes and leaves behind a reddish-brown stain.
Tear stains are not just a cosmetic issue. Constant moisture around the eyes can also encourage the growth of bacteria and yeast, such as Malassezia, which may lead to odor, skin irritation, and other health concerns. For that reason, identifying the cause of tear staining and taking appropriate action is important.
What Causes Tear Stains?
One of the main causes of tear stains is epiphora, a condition in which tears are produced excessively and overflow from around the eyes.
Normally, a dog’s tears drain through the nasolacrimal ducts located at the inner corners of the eyes and then pass into the nose. However, if these ducts become blocked or narrowed for some reason, the tears cannot drain properly and spill out of the eyes instead.
Common causes of epiphora include the following:
Genetic Factors
Brachycephalic breeds, such as Shih Tzus and Pugs, as well as dogs with large, prominent eyes, often have narrow or unusually shaped nasolacrimal ducts. As a result, tears may not drain smoothly.
Inflammation and Infections
One of the leading causes of epiphora is allergies. In particular, food allergies, such as reactions to certain proteins or grains, as well as environmental allergies, such as pollen or dust mites, can trigger excessive tear production. When allergies are involved, swelling may occur around the nasolacrimal ducts, making them more likely to clog and causing tears to accumulate around the eyes.
In addition, when the area around the eyes stays constantly damp, it can promote the growth of bacteria and yeast, especially Malassezia. This may inflame the skin around the eyes and worsen epiphora. In some cases, the eyes themselves may also develop infections.
External Environmental Factors
In urban or industrial areas, air pollutants such as fine particles and smoke can irritate a dog’s eyes and increase tear production. Dogs that spend a lot of time outdoors or live with windows open may be especially affected.
Household cleaning chemicals, scented sprays, and cigarette smoke can also irritate a dog’s eyes and contribute to epiphora. Inappropriate shampoos or grooming products may have the same effect.
Seasonal changes can also play a role. In spring and fall, allergens such as pollen and dust tend to increase, which may trigger eye irritation and excessive tearing.
Dental Health Issues
Dental disease, such as periodontal disease or oral inflammation, can also increase tear production. Because the tear glands and the oral cavity are closely connected through nerves and blood vessels, dental issues may sometimes contribute to tear staining.
Tear staining itself is not always a serious health problem. However, if left unaddressed, it may increase the risk of skin irritation and infection. That is why identifying the underlying cause and providing proper care is important.
The Impact of Daily Habits
Everyday habits can also affect tear staining. Drinking hard water or water high in minerals, such as iron or magnesium, may darken the color of tears. When these minerals accumulate in tears and adhere to the coat, they may oxidize and make reddish-brown stains more noticeable.
The Relationship Between Dog Food and Tear Stains
Diet quality, which directly affects a dog’s overall health, may also be related to tear staining. Poor-quality dog food may contribute to inflammation in the tear ducts, increasing tear production and deepening tear discoloration.
This is especially true when the food contains artificial ingredients or ingredients that may trigger allergies.
Providing an appropriate diet can help support the immune system and improve the health of the area around the eyes. It may also help reduce the allergies and inflammation that contribute to tear staining.
Ingredients to Avoid
| Ingredient Type | Why It Should Be Avoided |
|---|---|
| Artificial additives | Artificial colorings, preservatives, and sweeteners may cause inflammation as they are broken down in the body, which can worsen tear staining. Choosing ingredients made with naturally derived components is important. |
| Excess iron or magnesium | Porphyrin, the organic compound that affects tear discoloration, may increase when iron or magnesium levels in the body are excessive. This can make tears more prone to oxidation and make reddish-brown staining more visible. A well-balanced mineral profile is important in recipe design. |
| Low-quality filler ingredients | Fillers with low nutritional value, such as corn and soy, which are often found in lower-quality dog foods, may trigger allergies or digestive issues and worsen tear staining. |
Ingredients That May Help Reduce Tear Stains
① High-Quality Animal Protein
Dogs are considered carnivorous animals, and animal protein is said to be their primary energy source. High-quality animal proteins such as the following may help strengthen immune function and reduce inflammation.
| Ingredient | Potential Benefit |
|---|---|
| Lamb | Rich in iron and B vitamins, and commonly used in allergy-friendly dog foods. |
| Fish | Contains high levels of omega-3 fatty acids, which are believed to have strong anti-inflammatory effects. |
② Whole Grains and Omega Fatty Acids With Anti-Inflammatory Properties
Ingredients that may help reduce inflammation can also be useful for easing tear staining.
| Ingredient | Potential Benefit |
|---|---|
| Whole grains (brown rice, oatmeal) | Because they are unrefined, they are rich in antioxidants and dietary fiber. They may support digestion and help reduce inflammation. |
| Omega fatty acids (fish oil, flaxseed oil) | May help reduce inflammation around the eyes and support skin health. |
③ Ingredients Containing Probiotics and Prebiotics
Supporting gut health may improve overall immune function and help reduce the allergies and inflammation associated with tear staining.
Probiotics
Probiotics are beneficial bacteria—or foods containing them—that help maintain and increase healthy gut bacteria. When pets have sufficient levels of beneficial bacteria in their bodies, they are far less likely to suffer from diarrhea, constipation, vomiting, and other digestive issues.
As probiotic levels increase, nutrient absorption is improved, digestion stays healthier, and immune function is strengthened. Probiotics may also help fight viruses that cause infections. In addition, probiotics can produce vitamins such as B vitamins and vitamin K.
Prebiotics
A dog’s immune system is closely linked to digestive health. In fact, about 80% of the immune system is said to be associated with the digestive tract. With this in mind, it becomes clear that gut health plays an important role in disease prevention.
Prebiotics can help strengthen immunity by supporting a healthier gut environment. One study showed that puppies born to mother dogs supplemented with both prebiotics and probiotics during pregnancy tended to have stronger immunity.