Mastitis is a common problem in female dogs that have not been spayed. This condition is painful and can progress quickly, putting your dog at risk for abscesses, tissue damage, and systemic infections.  

Being aware of the early signs of mastitis in dogs can help you ensure that your dog receives treatment quickly if this condition develops.

What is Mastitis in Dogs?

Mastitis is an inflammation of the mammary gland. It most often occurs in dogs that have recently given birth but can also occur in dogs experiencing pseudopregnancy (false pregnancy).  

Mastitis can develop in one or several mammary glands and can range from mild to severe.

Mastitis is typically categorized as acute, chronic, or subclinical. Acute mastitis has a sudden onset and often presents with obvious clinical signs, such as a mammary gland that is visibly swollen and painful. Chronic mastitis is more subtle at the onset and symptoms may be mild at first and worsen over time. Subclinical mastitis is often asymptomatic, meaning there are no signs, and may only be detected when a mother’s puppies fail to grow at a normal rate.

Symptoms of Mastitis in Dogs

Dogs suffering from acute or chronic mastitis may experience one or more of the following symptoms:

• Mammary glands that are red, swollen, painful, or warm to the touch
• Mammary glands that are discolored or appear bruised
• Ulceration, abscesses, or gangrenous areas in the mammary tissue
• Decreased milk production
• Poor growth and decreased weight gain in puppies
• Discharge from the mammary gland, which may be discolored or bloody
• Loss of appetite
• Vomiting
• Lethargy
• Fever

Dogs with subclinical mastitis are often asymptomatic and may continue to feel and act normally despite the inflammation in the mammary tissue. 

How Do Dogs Get Mastitis?

Mastitis can occur with or without infection. In cases where mastitis is caused by an infection, bacteria enter the mammary gland by ascending through the teat (nipple) canal.  

Trauma to the nipples or mammary tissue or living in an unsanitary environment may increase the risk of developing mammary infections. In rare cases, fungal infections leading to mastitis have been reported.

Non-infectious cases of mastitis can develop secondary to galactostasis, or an absence of milk flow. This is most common in mother dogs after weaning or when puppies die and the mother dog is no longer nursing. Galactostasis can also occur if the puppies won’t nurse from all glands equally, or if an abnormality obstructs the flow of milk from a particular gland.  

Mastitis is most common in dogs that have recently given birth, but can also occur in dogs that have never been pregnant. Unspayed female dogs may experience pseudopregnancy, or false pregnancy, in which they develop symptoms of pregnancy such as mammary development and lactation, without actually being pregnant.  

Dogs experiencing pseudopregnancy can then go on to develop mastitis via the same mechanisms as pregnant dogs.

Diagnosing Your Dog with Mastitis

If you suspect your dog may have mastitis, you should seek veterinary care as soon as possible. Mastitis can worsen quickly, so prompt diagnosis is necessary to ensure the best outcome.  

Your veterinarian will likely recommend some or all of the following tests to confirm the diagnosis:

Physical Examination. Your veterinarian will perform a full physical examination on your dog, including palpating the mammary glands and taking samples of the milk.

Blood Work. Your veterinarian may recommend performing a complete blood count and biochemistry panel to look for signs of inflammation and infection. Blood work may also be recommended to look for underlying medical conditions that may have predisposed your dog to develop mastitis.

Milk Cytology. Your veterinarian will examine a sample of your dog’s milk under a microscope to evaluate the cell types present in the sample. This can be used to diagnose inflammation and may help your veterinarian determine whether an infection is present.

Milk Culture. If an infectious cause of mastitis is suspected, your veterinarian may submit a sample of your dog’s milk to a lab for culture. The sample will be used to grow colonies of the bacteria, which can then be identified so that appropriate treatment can be selected.

How to Treat Mastitis in Dogs

Timely treatment of mastitis is necessary to reduce the spread of infection and decrease the damage to the mammary tissue.  

If your dog is diagnosed with mastitis, your veterinarian may recommend one or more of the following treatments:

Antimicrobials. If an infectious cause for the mastitis is identified, antimicrobial medication will be prescribed to treat the infection. Ideally, antimicrobial drugs will be chosen based on the results of a milk culture. Most antimicrobials used in the treatment of mastitis do not pass into the milk, so it is safe for the puppies to continue nursing.

Pain Control.  Medications such as non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to manage pain and reduce inflammation in the affected mammary gland.

Cabbage Leaves.  Although we don’t know exactly why or how they work, cabbage leaves have long been used to treat swollen mammary glands. Applying raw cabbage leaves to the affected gland can reduce inflammation and speed recovery from mastitis.  The leaves can be held in place with gauze or a light bandage and should be changed every few hours.

Hand-Milking. In post-partum dogs who are still nursing puppies, milking the affected gland as frequently as possible can help flush the gland and improve blood flow. Applying warm compresses before milking can help.

Reducing Stimulation. In cases of pseudopregnancy, or when there are no puppies for the dog to nurse, it is best to allow the milk supply to dry up. Hand-milking should be avoided, and the dog should not be allowed to lick her own nipples. In some cases, medication may be prescribed to decrease milk production.

Hospitalization. In severe infectious cases of mastitis in dogs, bacteria can enter the bloodstream and cause sepsis, making your dog extremely ill. If this is the case, a dog may need to be hospitalized for intravenous fluids, antibiotics, and supportive care for several days.

Surgery. In rare cases, the affected mammary gland may be so damaged by the infection and inflammation that it must be removed. Most dogs recover well from mastitis-related surgery and can continue nursing puppies on the other unaffected glands.

Cost to Treat Mastitis in Dogs

Pet owners can expect to spend approximately $300-$800 on diagnostics and treatment for mastitis in dogs, depending on the severity of the disease. 

Severe cases requiring hospitalization or surgery will incur additional costs, which may range into the thousands depending on the severity of the disease.

Most cases of canine mastitis respond well to outpatient treatment. 

How to Prevent Mastitis in Dogs

The most reliable way to prevent mastitis is by spaying female dogs to prevent unwanted pregnancies and pseudopregnancies. Spaying also reduces the risk of developing other serious conditions such as mammary tumors and uterine infections.  

Male dogs should be neutered to prevent them from causing unwanted pregnancies in unspayed females.

In breeding females, mastitis can be prevented by maintaining a sanitary environment for the dog and her puppies. The whelping box should be kept clean and dry, and any bedding should be changed frequently.  

The nails of nursing puppies should also be kept trimmed to prevent trauma to the mother’s nipples, which can lead to mastitis. Puppies often develop a preference for a particular teat and should be encouraged to nurse on all glands to ensure good milk flow and prevent galactostasis.

Related Conditions

• Dog Pregnancy
• Galactostasis
• Mammary hyperplasia
• Pseudopregnancy