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Mastitis in Dogs: Causes, Signs, Diagnosis & Treatment

What exactly is mastitis in dogs, and why does it occur? How is mastitis in dogs diagnosed and how do you help a dog with mastitis?

Written by: Jennifer Lesser

Last Updated on January 19, 2024 by Dogster Team

Multiple puppies nursing on one mother dog.

Mastitis in Dogs: Causes, Signs, Diagnosis & Treatment

Whether you’re a responsible breeder or a pet parent to a female dog who just had puppies, mastitis in dogs is a condition that can impact any nursing canine. And, in some rare cases, mastitis in dogs can even occur in female dogs that aren’t new mamas. The pregnancy and birth process can be stressful for your dog — it’s no picnic for humans, either! — and as their breast glands are stimulated to begin producing milk for puppies, the physical toll of pregnancy and nursing combined with sharp little puppy teeth can create a hotbed of bacterial activity. If your dog’s immune system isn’t able to fight off that bacteria because she’s overly tired (as is anyone who just gave birth), lacks proper nutrition or her environment isn’t kept clean, an infection like mastitis can develop.

What exactly is mastitis in dogs?

Happy mother dog nursing her newborn puppies.
What is mastitis in dogs? Photography © JodiJacobson | E+ / Getty Images.

According to Dr. Kathy Staveley, a veterinarian at University Veterinary Hospital in Salt Lake City, Utah, mastitis literally means an inflammation of the mammary gland — and it may or may not be due to an infection. The condition is seen most commonly in female dogs who are nursing — or recently stopped nursing — and is caused by either bacteria that ascends up the nipple and causes infection of the gland, or trauma to the gland that results in inflammation and/or infection. “On rare occasions, this can also happen in dogs that are undergoing pseudopregnancy — a condition in dogs that causes pregnancy-related signs in the absence of true pregnancy,” she adds.

Dr. Heather Mitchell, associate veterinarian at Animal Health Clinic in Fargo, North Dakota, notes that mastitis in dogs can also develop secondarily, due to a condition called galactostasis, which is the failure of milk to become emptied from the teat canal. “Pet owners can help prevent mastitis after their dog gives birth by keeping the environment clean and removing any sharp edges that could potentially injure full mammary glands,” she adds.

How to prevent mastitis in dogs  

Puppies nursing from a mother dog.
How can you help prevent mastitis in dogs? Photography © GlobalP | Getty Images.

The good news, Dr. Staveley notes, is that mastitis is very rare in spayed dogs — so spaying female dogs is always the best prevention of mastitis in dogs. “We can help dogs that are lactating by ensuring that the puppies’ nails are kept short to minimize their trauma to the gland, ensure that all glands are being nursed, keep the dog in a clean and safe environment, and change bedding frequently,” she adds. 

Diagnosing mastitis in dogs

A puppy nursing on a mother dog.
Know the symptoms of mastitis in dogs. Photography © SariJuurinen | Getty Images.

According to Dr. Mitchell, one of the first symptoms of mastitis in dogs that pet owners may notice is that their dog develops a fever and loss of appetite. Upon further inspection, they may find inflamed, swollen, firm and painful mammary glands, and possibly discolored, thick or bloody milk. “Sometimes, the only abnormality noticed is that the puppies are failing to gain weight,” she adds.

If your pet has any of these symptoms, a visit with the veterinarian is necessary. “Mastitis can quickly turn into a severe condition if not treated promptly. If your mother dog is showing any signs of swelling, irritation, increased redness or pain in the mammary glands — or if the pups are having a difficult time nursing or failing to gain weight — please seek the help of your local veterinarian,” Dr. Mitchell urges.

She explains that your veterinarian can take a sample of the milk and look for abnormalities under the microscope, or even send a sample to the laboratory to check for growth of bacteria. An ultrasound of the mammary glands is another helpful tool to diagnose mastitis. “Often mastitis can be diagnosed with history and exam alone,” Dr. Staveley adds. “A recent history of nursing puppies and recent weaning or heat cycle with one or more symptoms is highly supportive.”

Treating mastitis in dogs

Puppies nursing from a mother dog.
How is mastitis in dogs treated? Photography © Tijana87 | Getty Images.

If your pet is diagnosed with mastitis and it’s due to bacterial infection, antibiotics and pain medication are necessary for treatment, Dr. Mitchell notes. If an infection is not present, the treatment will be symptomatic therapy involving pain control, applying warm compresses to the mammary glands and frequent expression of the milk from the glands.

Gentle massaging of the glands might also be helpful for treating mastitis in dogs.

“Treatment varies depending on the severity of the condition, but most dogs are treated with antibiotics for the underlying bacterial infection, pain medication, and encouraging milk let down and production,” Dr. Staveley concludes. “Puppies can usually continue to nurse, or the gland can be hand-milked. Local therapy to the gland can include massage, warm compress or even raw cabbage leaf compress.”

Featured Image Credit: cmannphoto | iStock / Getty Images.

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