Mastitis in Dogs

Autumn Madden, DVM
By Autumn Madden, DVM on Mar. 7, 2022
Mother Labrador Retriever feeds her puppies

In This Article


What is Mastitis in Dogs?

Mastitis is an inflammation of the mammary glands in female dogs. It can occur with or without infection. Typically, mastitis occurs postpartum, due to how messy the whelping box can get and/or weening the pups abruptly or too early. There are multiple types of mastitis in dogs.  

Acute Mastitis: Sudden swelling of the mammary gland that includes heat and pain. The milk will be obviously abnormal. This type of mastitis may also cause changes in the mother, such as lethargy.  

Septic Mastitis: Sudden swelling of the mammary gland associated with heat, pain, abnormal milk coloration, and changes in the mother such as lethargy, changes in appetite, fever. Septic mastitis and its symptoms are typically caused by bacteria.  

Chronic or Subclinical Mastitis: Long-term inflammation of mammary tissue accompanied by a lack of obvious clinical signs such as swelling or warmth.  

Non-septic Mastitis: Inflammation of the mammary tissues without a cause such as bacteria or fungus.  

Gangrenous Mastitis: The teat, and possibly surrounding tissues, appears black or bruised. The milk may be blood-tinged or bloody. The mother will also be very ill, with symptoms such as vomiting, decreased appetite, fever, changes in blood pressure. 

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Symptoms of Mastitis in Dogs

The symptoms of mastitis vary, depending on the type of mastitis. Affected glands will have milk or fluid that may be described as discolored, bloody, or pus-like in appearance. If they are infected, glands may be described as swollen, warm, firm, discolored, or ulcerated (skin broken open).  

Acute mastitis symptoms may include glands that are hot and painful. This condition may progress to septic mastitis if it’s not treated in time. In septic mastitis, clinical signs include fever, depression, anorexia, lethargy, or mother neglecting puppies.  

The only clinical sign observed with chronic or subclinical mastitis is failure of the pups to thrive. For non-septic mastitis, which commonly occurs at weaning about 3-4 weeks after birth, common signs include swollen glands that are painful to touch, even though the dog is relatively healthy and alert.  

In severe cases of mastitis, the mother will be sick and may show symptoms such as: 

  • Fever 

  • Refusal to eat 

  • Vomiting 

  • Listlessness 

  • Rapid heart rate 

  • Depression 

  • Severe drop in blood pressure 

Causes of Mastitis in Dogs

Mastitis is most commonly caused by bacteria, such as E. coli, enterococci, staphylococcus, and streptococcus spp. Other causes include: 

  • Fungus, such as blastomycosis and mycobacterium 

  • Trauma, such as a wound caused by sharp edges of the whelping box or (rarely) a puppy scratching the teat while nursing 

  • Damp and unsanitary environment 

  • Prolonged milk stasis, or a build-up of milk 

  • Septicemia, or sepsis 

  • Death of newborn puppies 

How Veterinarians Diagnose Mastitis in Dogs

Mastitis is typically diagnosed with a physical exam and any information pet parents can provide to a veterinarian. After a physical exam and history have been taken, further diagnostics are done to confirm the severity and type of mastitis so the appropriate course of treatment can be selected. Additional imaging may be done to determine the extent of injury and the critical nature of the condition.  

Blood work such as a CBC and biochemistry may be done to rule out: 

  • Elevated white blood cell count (WBC), which can indicate a severe case of mastitis 

  • Platelet abnormalities, which can indicate gangrenous mastitis and sepsis 

  • Dehydration 

A cytology procedure may be done, which can reveal an increase in white blood cells and either bacteria or fungus (rare). During a cytology study, the vet will examine groups of cells to detect abnormalities.  

A culture of the milk or fluid from the gland may be sent off so the veterinarian will know which medications to prescribe. Radiographs (x-rays) may be done to confirm or rule out gangrenous mastitis. An ultrasound may also be done to determine if there have been any abnormal changes in blood flow or tissue definition. Samples of tissue may be taken and sent to a lab for evaluation (biopsy/histopathology) to confirm mastitis and not cancer.  

Treatment of Mastitis in Dogs

Treatment depends on the type and severity of the mastitis. Severe cases require hospitalization along with IV fluids, pain medication, and antibiotics. Surgical therapy may be needed for necrotic (dead) tissue, as this must be drained, flushed, and removed. Antibiotic therapy tends to last for 2-3 weeks. 

Acute mastitis is treated using broad-spectrum antibiotics, and chronic mastitis is treated based on culture and sensitivity results. Because mastitis affects both mom and puppies, mom is started on antibiotics based upon the pH of the milk or fluid expressed from the gland until the culture results from the cytology come back from the lab. It is important to know the age of the puppies and if they are still nursing, as there are some antibiotics that may be harmful to them. 

In addition to oral medication, topical therapy will be needed. If the mother is still nursing, the infected glands are milked by hand every 6 hours until signs of inflammation (e.g., heat, swelling, redness, pain) improve. Prior to milking, warm compresses may be applied to encourage drainage. 

If the gland is minimally painful, a massage may be done to encourage blood flow and help break up congested tissue. Cold laser therapy may be recommended to help reduce pain and inflammation. Cold laser therapy is helpful because it is a noninvasive procedure that uses a specific frequency of light to stimulate tissue healing and improve blood circulation to specific areas such as the skin and mammary tissue.  

Cabbage compresses may also be done to decrease inflammation. Not much is understood about what makes cabbage so helpful, but it is believed that a cabbage compress can be beneficial because it acts as an effective cold compress to relieve mild inflammation. This therapy may be done in the clinic if the mother is hospitalized, or it may be recommended as part of at-home care. After treatment with cabbage compresses, puppies can nurse from affected glands when wraps are removed. 

Continuing to nurse puppies prevents milk stasis and helps with drainage. If the mother is currently taking antibiotics, probiotics may be helpful to the mother and puppies to help maintain gut flora and prevent diarrhea. 

When treating mastitis, there may be cases in which puppies must be weaned early or an alternative source of nutrition provided, including: 

  • Multiple glands are abscessed 

  • An antibiotic is needed that is unsafe in neonates 

  • Mother is systemically ill 

  • Mother refuses to nurse 

Treatment of mastitis associated with a phantom pregnancy may include antibiotic therapy and cabbage leaf therapy. Phantom pregnancy is also known as pseudopregnancy or false pregnancy. This occurs when a dog displays maternal behavior in combination with the physical signs of heat followed by signs of pregnancy, without being pregnant. This behavior can be observed in an intact female dog and is treated by removing the object (e.g., toy, blanket) that is being “mothered.” 

Recovery and Management of Mastitis in Dogs

If a dog is diagnosed with either acute or chronic mastitis, the prognosis is good. Clinical signs should clear up in about 2-3 weeks in response to treatment. If the mastitis is not responsive to treatment or there is gangrenous mastitis associated with septicemia, the prognosis is guarded.  

The following steps can help reduce the right of mastitis: 

  • Trimming puppies’ nails to reduce wounds to the mother that may lead to infection. 

  • Monitoring neonates to make sure they are nursing from all glands to avoid sudden and prolonged milk statis. If neonates are not nursing from all the glands, it is OK to move them around. 

  • Keep the area where mom and puppies are kept clean, dry, and free of sharp edges to prevent an environment where bacteria can thrive 

  • Change bedding in nursing environment at least 1-2 times per day and scrubbing the box daily to reduce bacteria. 

Mastitis in Dogs FAQs

Can I treat mastitis in dogs at home?

Mastitis must first be diagnosed by a veterinarian so a treatment plan can be put together for the mother and possible affected puppies. Moderate to mild cases may be sent home with a regimen of antibiotics, care modifications, compression therapy, and possibly massage. Treatment should not be done at home without the supervision of a veterinarian, because therapy can include hospitalization, surgical treatment, medication, and/or massage/compression therapy.

Is mastitis in dogs fatal?

Yes, mastitis can be fatal for the mother and/or the puppies if not addressed promptly.


  1. A. Memon, Mushtaq. Merck Veterinary Manual. Mastitis in Small Animals - Reproductive System.  

  1. K., Rothrock, et al. VIN: Veterinary Information Network. Mastitis (Canine). ‌ 

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Autumn Madden, DVM


Autumn Madden, DVM


I am from Washington, DC, and I wanted to be a veterinarian since watching my uncle on his farm at 8. I graduated from Tuskegee University...

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