Dog Tear Stains: Porphyrins' Roll in Eye, Mouth, And Fur Coat Stains
- Everwell Pets
- 3 days ago
- 6 min read
Causes, Treatment, & Prevention
You’ve probably noticed that reddish-brown staining beneath the eyes of a light-colored dog, or along a damp muzzle, and asked yourself: “What’s going on here?” In many cases the culprit is not a pigment we commonly focus on, but a group of compounds called porphyrins. In this blog we’ll unpack the story of porphyrins in dogs: what they are, how and why they show up, and practical and holistic strategies to minimize their impact.
What Are Porphyrins?
Porphyrins are iron-containing molecules produced during the breakdown and synthesis of heme, the component of hemoglobin that carries oxygen in red blood cells[1].
In simpler terms: when red blood cells break down, or when the body is generating new ones (or dealing with metabolic or toxic stress), porphyrin compounds are released or accumulate.
In dogs, these molecules can be excreted in several ways—through bile, urine, tears, and even saliva—but the preferred excretion pathway is through the bile and digestive system.
How Are Porphyrins Released From The Body
The liver takes the lead role in cleaning up old red blood cells. It breaks down hemoglobin into bilirubin and related compounds, which are then packaged into bile. Bile is produced by liver cells, stored in the gallbladder, and released into the small intestine after meals to help digest fats. As bile moves through the intestines, it carries porphyrins and other waste products out of the body through the stool.
This route—via the liver, gallbladder, and intestines—is the body’s most efficient way of clearing porphyrins. When the liver or bile flow is sluggish, or when toxins or inflammation slow this process, the body relies more heavily on secondary exits like tears, saliva, or urine. That’s when we start to see porphyrins in visible places—around the eyes and mouth, or on the body where the pet may be licking.
Depending on breed, coat color, tear drainage anatomy, and overall health, these porphyrins can stain fur or skin-fur junctions reddish-brown. Even if no major disease is present, this visible staining often signals that the body’s detoxification pathways or organ support systems—especially the liver and gallbladder—could use a little extra attention[4].
How Are Porphyrins Produced ?
Dogs naturally produce porphyrins as part of normal red blood cell turnover and heme metabolism. When everything is in balance, the porphyrin load is low, and excretion is efficient.
However, certain factors increase the load or slow clearance:
Anatomical and grooming factors: in light-colored breeds, porphyrins may collect in pooled or poorly drained tears or saliva and show up as reddish-brown stains [4].
Underlying infections or mild inflammation of tear ducts or eyelids that increase tear production or poor drainage[4].
Liver involvement: some drugs or toxins can induce hepatic porphyria in dogs[3].
Inherited forms of porphyria (very rare), such as congenital erythropoietic porphyria or protoporphyria[1].
In many cases of cosmetic tear-staining (commonly attributed to porphyrins), the dog is otherwise healthy, but the stains signal that there is more porphyrin than usual or slower removal of it.
Tear Stains, Muzzle Stains, & Stains On The Coat
Porphyrin staining isn’t limited to the eyes or muzzle. Many pet parents notice the same reddish-brown discoloration on their dog’s paws, front legs, inner thighs, or even under the tail. These areas often have one thing in common—excessive licking.
When a dog repeatedly licks an area, saliva saturates the fur, leaving porphyrin pigments behind as it dries. Over time, these compounds oxidize and darken, producing the familiar rusty-red hue. You’ll often see this on white or cream-colored dogs who obsessively lick their paws from allergies, yeast overgrowth, anxiety, or joint pain [5].
Addressing the root cause of the licking is key:
Allergies (environmental or food) often lead to itchy paws and recurrent licking. Always keep in mind that if more than one limb is affected, allergies are likely the culprit—but if only one limb is involved, it’s usually a chiropractic issue rather than allergies. (Read more about canine allergies here.)
Yeast or bacterial overgrowth can cause damp, irritated skin that perpetuates the cycle.
Arthritis, radiculopathy, or peripheral neuropathy—pain or numbness traveling down a limb due to spinal subluxation—may cause a dog to lick or chew the affected area for relief. This often indicates the need for a chiropractic adjustment to restore proper nerve flow and reduce discomfort. (Read more about Canine Arthritis here).
Behavioral factors such as boredom, stress, or anxiety can also contribute. This helps explain why I often see more reddish staining in our senior population—reduced liver function and increased anxiety are both common with age, which can slow detoxification and amplify porphyrin buildup in the saliva and then on the fur.
Managing these triggers—whether through diet adjustments, targeted supplementation, skin support, chiropractic care, or calming strategies—will not only reduce the licking but also help the stains gradually fade as new fur grows in.
Managing Porphyrins from the Inside Out: A Functional Approach to Red Staining
Age-old advice says to wipe your dog’s face—especially around the eyes and muzzle—at least twice daily with a slightly damp cloth to remove tear film or saliva that carries porphyrins, and keep the fur in these areas neatly trimmed so tears can drain properly instead of pooling[4]. Most pet parents instinctively do this, but in my experience, I’ve rarely seen this grooming habit make a meaningful difference in reducing the reddish appearance. The true solution lies in supporting internal balance—especially liver function and detox pathways.
Use stainless steel or ceramic food bowls rather than plastic, which can harbor bacteria that irritate the face and eyes[4]. And not just for this issue—you should always choose stainless steel or ceramic bowls for many reasons, including reducing exposure to microplastics and chemical leaching that can burden your pet’s detox systems over time.
If staining is due to licking—whether on the paws or another area of the body—consider it pain-related and have your pet evaluated and adjusted by a certified animal chiropractor, or look into possible yeast overgrowth. The easiest and most effective first step is to remove all carbohydrates, sugars, and starches from the diet. If you’re feeding an ultra-processed diet, transition to a frozen raw, species-appropriate diet to help rebalance the gut and reduce inflammation.
Feed a frozen raw, species-appropriate diet (more about the many benefits of raw food here) to support liver function, gut health, detoxification, immune balance, and reduce inflammation.
Provide only filtered or reverse osmosis water, ensuring the filtration system removes chlorine and fluoride. We—and our pets—should never drink unfiltered tap water, as it often contains contaminants and chemicals that can burden the liver, thyroid, and overall detox pathways.
A supplement to consider is a product called Angel Eyes Tear Stain Powder. You can find it here. Note that they also offer a tablet form, but we don't recommend that form due to the list of inactive ingredients. Our client experienced success with this, but it does take some time, so consider at least a month. This will not "lift" the stains out of the coat, but with grooming of the stained fur and supplementation, the stains cleared up.
Pet parents should pay attention if staining suddenly appears, deepens in color, or becomes excessive, as this can signal chronic eye irritation, allergies, or tear duct issues, especially in brachycephalic breeds. If redness, discharge, or other changes accompany the staining, it’s best to have your veterinarian check for infection, structural drainage problems, or underlying liver stress.
In Conclusion
Porphyrins in dogs are a natural byproduct of metabolism that sometimes overstay their welcome. When excreted through tears or saliva, they can stain light fur reddish-brown—most often around the eyes, mouth, or wherever a dog licks excessively. While the majority of cases are cosmetic, porphyrin staining can reveal small imbalances in drainage, hygiene, or structural health.
Simple habits like switching to a frozen raw dog food diet and using only filtered water can make a world of difference. If stains persist or are accompanied by other signs, a deeper look may be warranted.
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Citations:
Merck Veterinary Manual. Congenital Erythropoietic Porphyria and Protoporphyria in Animals.
Greijdanus-van der Putten et al., Toxicol Pathol (Drug-Induced Protoporphyria in Beagle Dogs). PubMed
MedVet. Everything You Need to Know About Tear Staining in Dogs.
Rau Animal Hospital. A Veterinary Guide to Stubborn Tear Stains on Dogs.
Dogs for the Earth. What Are Porphyrins in Dogs?