Mammary Inflammation (Mastitis) in Dogs

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Last updated on
6 min read

Key takeaways

Mastitis is the inflammation of breast (mammary) tissue.

  • Mastitis in dogs usually results from a bacterial infection and almost exclusively affects nursing mothers
  • Severity ranges from subclinical, with no symptoms, to life threatening
  • Severe mastitis can be fatal to the mother and/or pups
  • Common symptoms are: swollen, hard, and/or hot teat(s), pups not gaining weight, and abnormal milk
  • Mastitis is diagnosed with a physical exam, milk culture and/or blood work
  • Infection often results from a dirty environment and trauma to a teat
  • Mastitis is not contagious to humans or other pets, but it’s possible for infectious agents to pass to the puppies when they nurse
  • Mild cases respond well to treatment, clearing up within 2-3 weeks
  • In advanced cases the prognosis is guarded
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A closer look: Mammary Inflammation (Mastitis) in Dogs

Mastitis occurs almost exclusively in nursing females. It is most likely to occur during weaning, especially if weaning is forced or abrupt.

Healthy milk production requires regular demand from nursing. If not regularly drained, the milk backs up and can be very painful for the mother. This swelling alone can be the cause of mastitis because engorged gland(s) are also more susceptible to infection.

Mastitis from lack of milk flow has a good prognosis, with most dogs responding quickly to treatment.

Mastitis from a bacterial infection, if left untreated, can enter into the main bloodstream and lead to sepsis. In these instances the infection can be fatal to the mother and her pups. When caught early, the prognosis is good.

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Risk factors

Mastitis can affect multiple glands. Severity of mastitis ranges from subclinical to life threatening. Some dogs may not have any symptoms, while others become septic and may die.

Signs of worsening mastitis include

  • Vomiting
  • Behavioral change toward pups
  • Teat and surrounding tissue look black, cracked open, or bruised

If the teat looks abnormal, this is an EMERGENCY requiring immediate veterinary care.

Nursing mothers are at risk of mastitis, especially if weaning is forced/abrupt, if hygiene in the mother’s den is not sufficient, or if there has been injury to one of the teats.

Possible causes

Mastitis may be caused by:

  • Trauma to the teat
  • Damp, unsanitary environment
  • Bacterial infection
  • Abrupt/forced weaning
  • Prolonged milk stasis

Main symptoms

Testing and diagnosis

Diagnosis begins with a physical examination of the mother.

Other tests to determine the cause of mastitis include:

  • Cytology or fine needle aspirate
  • Ultrasound
  • Radiograph
  • Examination of milk or blood from the teat under a microscope
  • Blood work

Steps to Recovery

In rare cases when mastitis leads to sepsis, hospitalization may be necessary. Surgery may also be required. Dogs that reach this level of infection have a guarded prognosis and the mother may lose functional use of the gland.

Mild mastitis is often treatable at home. The main goal is to get milk flowing from the affected gland(s). A warm compress applied every few hours will encourage drainage. Using cabbage leaves in a compress may also relieve inflammation. If not too painful for the mother, gently massaging the teat and hand milking will help break up congested tissue and clear the gland. Pups are also encouraged to nurse from the teat.

It is best to consult a vet before trying home remedies or encouraging pups to nurse from an inflamed teat.

Broad-spectrum antibiotics are used to treat bacterial mastitis. Depending on the severity of the infection and the age of the puppies, it may be necessary to remove the puppies from the mother and use an alternative method for feeding them.

Dogs experiencing mastitis in association with a false pregnancy (pseudo pregnancy) also benefit from cabbage leaf therapy and antibiotics. Stimulating milk flow is undesirable in these cases as there are no pups to feed, so hand milking or massaging the gland(s) are not recommended. Removing any objects the dog is “mothering” is recommended to help shut down the milk production process.

For acute, mild cases the prognosis is good. Symptoms dissipate within two to three weeks with proper treatment.

In severe cases where the infection has spread to sepsis, the prognosis is more guarded.

Some dogs have chronic mastitis: long-term inflammation but the dog shows no symptoms. These mild cases are not usually life threatening unless the condition advances.


The definitive prevention of mastitis is sexual alteration (spaying) of female dogs to prevent pregnancy. In cases where this is not an option, the following strategies can help prevent mastitis in nursing mothers:

  • Maintain a clean and dry whelping den
  • Routine physical examination of mother, especially when weaning
  • Trim puppies’ nails
  • Encourage pups to suckle from all teats - move them around if needed

This condition is not contagious, but infectious agents can pass from the mother to the pups during nursing.

Is Mammary Inflammation (Mastitis) in Dogs common?

Mastitis occurs primarily in intact female dogs and almost exclusively in nursing mothers. It may also develop during late stages of pregnancy, or with a false pregnancy.

Typical Treatment

  • Antibiotics
  • Warm Compress
  • Cabbage leaf therapy
  • Encourage pups to suckle from infected teat(s)
  • Hand-milking if pups not available
  • Pain medication
  • Gentle massage of teat
  • Hospitalization
  • IV fluids
  • Surgery

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