Rust colored stains on a dog’s fur can have several potential causes. Determining the exact cause requires an examination by a veterinarian. However, some common reasons for rusty colored stains on a dog’s coat include:
Saliva Stains
Dogs naturally drool and lick themselves, which can lead to reddish-brown stains around their mouths. This occurs when porphyrin, a pigment found in saliva, tears, and other body fluids, oxidizes and turns rusty colored when exposed to air. Areas where dogs commonly develop these stains include:
- Around the lips and mouth
- On the paws and legs from licking
- On light colored fur under the eyes
Saliva stains are harmless but unsightly. Keeping the dog’s face folded and cleaning stains promptly can help reduce their occurrence.
Yeast Infections
Skin yeast infections, caused by overgrowth of Malassezia yeast, can lead to reddish-brown discoloration of a dog’s skin and fur. Areas commonly affected include:
- Paws
- Folds of skin
- Ears
- Armpits
- Groin
In addition to color changes, yeast infections cause flaky, greasy skin and itching. Treatment includes antifungal medications prescribed by a vet.
Acidic Urine
Urine stains on a dog’s fur can range from yellow to orange, reddish, or brown. The color depends on concentration, how long it has been there, and pH. More acidic urine has a darker, rusty appearance. Acidic urine can result from:
- Urinary tract infections
- Kidney or bladder stones
- Kidney disease
- Certain medications
- Special diets
Any urinary tract problems that cause frequent urination or leakage should be evaluated by a veterinarian. Stains can be managed by cleaning the fur promptly.
Anal Gland Problems
Rust colored stains around a dog’s rear end may come from impacted anal glands. These glands naturally express small amounts of brownish secretions when a dog defecates. However, if they become overfull and leak, they can stain the fur near the anus. Signs of an anal gland problem include:
- Scooting rear end along the ground
- Excessive licking of the area
- Unpleasant “fishy” odor
A vet can express the anal glands and provide treatment to prevent impaction if this is an ongoing issue.
Flea Dirt
Flea infestations can lead to dark specks of dried blood and feces called flea dirt. This debris can mat and stain the dog’s fur rusty brown or black. Signs of fleas include:
- Itching and skin irritation
- Red bumps
- Seeing fleas jumping on skin
- Tapeworm segments near anus
Treatment requires eliminating fleas from the dog and environment using flea prevention products.
Seborrhea
Seborrhea is a skin condition that causes flaking, redness, and greasiness of the skin. It can involve reddish-brown discoloration of the skin and fur. Seborrhea has several causes, including:
- Allergies
- Parasites
- Fungal or yeast infections
- Skin disorders
- Hormonal abnormalities
Finding the underlying cause is important for proper treatment of seborrhea outbreaks.
Allergies
Allergic reactions can cause reddish-brown staining of fur through a combination of factors such as chewing, licking, skin infections, and seborrhea. Saliva stains may occur as a result of excessive licking of irritated areas. Common allergens for dogs include:
- Flea bites
- Food
- Pollen
- Dust mites
- Mold
Identifying and avoiding allergens, while controlling secondary skin infections, is key to managing allergic dogs.
Trauma
Injuries that damage blood vessels or cause bleeding in the skin can lead to rust-colored staining of the fur. This often occurs along with scrapes, wounds, hematomas, or bruising of the skin after trauma. Common causes include:
- Scratches from other animals
- Cuts from sharp objects
- Burns or scalds
- Blunt force injury
The stain remains until the damaged skin has healed and new fur grows in. Cleaning the area promptly can help minimize lasting discoloration.
Sun Exposure
Some white or light-coated dogs can develop rust-colored fur staining after prolonged sun exposure. The sunlight oxidizes and alters pigments in the fur over time. Breeds prone to this phenomenon include:
- Poodles
- Bichon Frises
- Shih Tzus
- Maltese
Using dog-safe sunscreen and limiting intense sun exposure helps prevent fur staining.
Giardia Infection
The intestinal parasite Giardia can cause loose, greasy stools that stick to a dog’s fur and stain reddish-brown. Giardia spreads through ingesting contaminated fecal matter. Signs include:
- Soft, foul-smelling stool
- Gassiness
- Weight loss
- Lethargy
A vet can test for Giardia and provide medication to clear the infection.
Cushing’s Disease
Excess cortisol levels in dogs with Cushing’s disease can lead to skin thinning and hair loss. As the skin becomes exposed, secretions, urine scald, trauma, sun exposure, and infections can cause rust-colored staining. Other signs of Cushing’s include:
- Increased thirst and urination
- Panting
- Pot belly
- Skin infections
Cushing’s requires lifelong treatment with medication, sometimes along with radiation therapy.
Acanthosis Nigricans
This skin condition causes thick, dark, velvety patches on the skin that can extend to the fur. It results from high insulin levels and is often associated with diabetes or obesity. The skin in affected areas appears dirty or stained reddish-brown.
Medications
Certain medications like phenylpropanolamine used to treat urinary incontinence can cause rust-colored urine stains. Antibiotics like nitrofurantoin can also discolor urine. Any changes should be discussed with your veterinarian.
Hair Dyes
Some owners intentionally apply hair dyes or colored gels to their dogs. These can turn the fur red, brown, or other shades. However, dyes are often toxic if ingested, so they are not recommended.
Senile Sebaceous Adenitis
This condition of older dogs involves atrophy of sebaceous glands in the skin. It leads to dry, scaly skin with a rusty tinge. Hair loss and secondary skin infections can occur. It is managed with fatty acid supplements, antiseborrheic shampoos, and antibiotic treatment if infected.
Liver Disease
Severe liver dysfunction can cause jaundice and orange-brown discoloration of a dog’s skin, gums, and the whites of the eyes. This is due to a buildup of bilirubin from the failure to excrete bile. It requires evaluation by a vet.
Hemangiosarcoma
This is an aggressive cancer of blood vessel cells. It can cause bleeding tumors just under the skin, leading to rust-colored stains. Internal tumors may cause collapse from bleeding. This cancer requires chemotherapy, surgery, or palliative care.
Melanoma
Melanomas are dark pigmented skin cancers that can arise on a dog’s fur or skin. They may bleed or ulcerate, leading to rusty colored stains. Surgery is the main treatment but has a guarded prognosis long-term.
Copper Storage Disease
Buildup of excess copper in the liver can lead to rust-colored urine stains in dogs. It is an inherited condition seen mainly in Bedlington Terriers. Signs include jaundice, liver disease, and neurological problems if left untreated.
Conclusion
In summary, rusty colored stains on a dog’s coat can have many causes ranging from harmless to serious. Saliva stains are the most common and benign explanation. However, medical conditions like infections, cancers, trauma, liver disease, and others may require prompt veterinary attention. Getting an accurate diagnosis through lab tests and veterinary exam is important to determine appropriate treatment.
| Cause | Location | Other Signs | Diagnosis/Treatment |
|---|---|---|---|
| Saliva stains | Mouth, eyes, paws | None | None needed |
| Yeast infection | Paws, folds, ears | Itching, greasy skin | Exam, fungal culture, antifungals |
| Acidic urine | Groin, legs | Frequent urination | Urinalysis, urine culture, antibiotics |
| Anal gland issue | Near anus | Scooting, licking, odor | Exam, gland expression |
| Flea dirt | Base of tail, groin | Itching, fleas visible | Flea treatment |
| Seborrhea | Back, flanks, belly | Flaking, greasiness | Exam, skin scraping, treatment per cause |
| Allergies | Paws, groin, armpits | Itching, licking | Exam, allergy testing, avoiding allergens |
| Trauma | Depends on injury | Wounds visible | Wound care |
| Sun exposure | Face, back, sides | None | Prevention, limiting sun |
| Giardia infection | Around anus | Soft stools, weight loss | Stool exam, metronidazole |
| Cushing’s disease | Belly, groin, armpits | Increased thirst/urination | Blood tests, lifelong treatment |
| Acanthosis nigricans | Armpits, groin, neck | Dark velvety skin | Screen for diabetes |
| Medications | Groin, legs | Recent medication | Discuss with vet |
| Hair dyes | Applied area | Recent dyeing | Discontinue use |
| Senile sebaceous adenitis | Back, tail base | Scaly skin, hair loss | Fatty acid supplements |
| Liver disease | Skin, gums, whites of eyes | Jaundice, vomiting | Exam, liver function testing |
| Hemangiosarcoma | Depends on tumor site | Bleeding, collapse | Biopsy, chemotherapy |
| Melanoma | Skin, mouth, nails | Dark skin mass | Biopsy, surgery |
| Copper storage disease | Groin, legs | Jaundice, neurological issues | Genetic testing, copper chelation |