Canine Mastitis

Updated September 28, 2018
mother dog and puppies sleeping

Canine mastitis is typically associated with dogs who are nursing puppies, but this isn't always the case. Learn more about this painful condition, its causes and treatment.

About Canine Mastitis

Mastitis is essentially a bacterial infection of the milk ducts in a dog's mammary glands. You'll know your dog has mastitis once your veterinarian confirms it, but learn the signs and symptoms so it can be caught and diagnosed early.

Mastitis and Nursing Dogs

When a dog becomes pregnant, her body gears up to support the litter, and this includes producing milk for the pups to nurse. After the pups are born and begin nursing, sores, cracks and scratches sometimes form as the nipples become tender from the activity. This opens a pathway for bacteria to enter one or more ducts which leads to painful, irritated nipples. Under normal circumstances, the immune system is able to combat the invading bacteria, but sometimes the immune system is overwhelmed and the bacteria get a foothold in the tissue and a mastitis infection develops. Chances of contracting an infection are higher if the female is rearing her litter in unsanitary conditions.

Mastitis in Other Dogs

All of that said, a dog does not have to be pregnant or nursing in order to contract a mastitis infection. Any dog, including male dogs, can experience this condition. In cases such as this, cancer of the mammary glands is another possible cause for the condition. Dog breast cancer is an extremely serious condition; it's one that should be checked for immediately. Female dogs experiencing a "false pregnancy" can also develop mastitis.

Symptoms of Mastitis in a Dog

Spotting the signs of a mastitis infection is crucial to providing early treatment that will not only save your female a great deal of discomfort, it could save her from a more serious blood infection. Symptoms to watch for include:

Chihuahua with mastitis
  • Sudden loss of appetite
  • Fever and lethargy
  • Aggressive behavior (Caused by pain)
  • Tenderness of one or more breasts
  • An abscess or infected-looking scratch near the nipple
  • Redness, heat, swelling and hardness of the affected breast(s)
  • Teats may swell up considerably and become engorged
  • Dark discoloration of the affected breast(s)
  • Discolored milk
  • Foul-smelling pus discharge from the nipple

Early Signs of Mastitis

The symptoms that you should watch for as early signs your nursing dog may have mastitis is the daily weight of the puppies. If they are not gaining weight as quickly as they should, this means the mom may be developing mastitis. Other than some mild discomfort, a dog may not show signs until she's developed a strong case of mastitis, and tracking your puppies' daily weight gain is a good way to catch mastititis early. For non-nursing dogs, the first signs of onset will be some swelling and redness around the nipples.

Signs Puppies Are Nursing From a Dog With Mastitis

Puppies themselves will show signs of drinking infected milk. Symptoms include:

  • Distressed behavior (Crying, restlessness)
  • Dehydration
  • Weight loss
  • Eventual lethargy followed by death

How Mastitis Is Diagnosed

Diagnosing a case of canine mastitis is relatively straightforward. The vet will gently examine the dog's breasts to determine if one or more teats are infected. In addition to looking for the signs listed above, the vet may try to carefully express the breast to check for the presence of pus if it isn't already visible due to leakage. He or she may also do a fine needle aspiration to draw milk or pus from the nipple. Your veterinarian will also do blood tests, bacterial cultures and a milk cytology to look for the presence of infection and confirm that your dog has mastititis.

Canine Mastitis Treatment

Left untreated, the infection can lead to septic shock and death. If you suspect your dog may have a mastitis infection, call your vet immediately to report what you've observed. Treatment for a canine mastitis infection largely depends on how far the infection has progressed. If it's caught in the early stages, repeated expressions may be enough to remove the contamination, but it's best to let your vet decide what your dog needs. Common treatments include one or more of the following:

  • Applying warm, moist compresses to the affected breast - This increases circulation and may make it easier to express the nipple and get the milk flowing. This in turn relieves pressure and reduces pain.
  • Soaking up the infected milk and any pus discharge with a paper towel and throwing it away - This is an important sanitary measure.
  • Administering antibiotics - This helps remove any remaining traces of the bacterial infection. Your veterinarian will typically prescribe a broad-spectrum antibiotics such as trimethoprim/sulfadiazine (Tribrissen®), lincomycin (Lincocin®), ampicillin (Polyflex®) or cephalexin (Biocef®, Keflex® or Keftab®).
  • Performing a mastectomy - This is a last resort to remove severely infected tissue and bring an end to chronic mastitis infections. Canine mastitis rupture treatment

Hospitalization and supportive care measures may be necessary in conjunction with any of these treatment methods.

Canine Mastitis Rupture Treatment

If the mastitis progresses without proper treatment the breasts can rupture. In this event your veterinarian will place your dog on antibiotics and monitor her condition. Veterinarians often do not close up the ruptured area to prevent more abseceses from forming.

Caring for the Litter

If a dog develops mastitis while nursing puppies, this raises special concerns for:


Since the infected milk makes the puppies sick, it is necessary to wean the pups off mom and begin bottle-feeding them with puppy milk replacement formula unless they are old enough to be weaned on to puppy food. Nearly all pet supply stores sell this formula as well as nursing kits that come with a bottle, nipple and nipple brush. The formula label provides mixing directions as well as information about how much you should feed each pup, according to its weight, and how far apart to space those feedings.


Additionally, you may also have to take over cleaning the pups if their mother loses interest in them. This means you'll need to help them relieve themselves until their bodies are developed enough to eliminate waste on their own. You can easily do this by wiping their genitals and anus with a baby wipe to stimulate elimination. This is only necessary for the first few weeks of life until you observe the pups begin to eliminate without your help.

Canine Mastitis Home Treatment

There are some options for treating canine mastitis at home, but you should discuss these with your veterinarian first particularly since the infection can become serious before few symptoms appear. Some treatments you can try include:

  • Cold compresses on the nipples soaked in Calendula.
  • Warm compresses combined with manually inducing milk from the nipples to empty them.
  • Using salves on the nipples to keep them from becoming irritated and chapped, such as petroleum jelly like Vasoline, cortisone spray or cream or a tincture of St. John's wort.
  • Some breeders hold cabbage leaves on the inflamed area for 10 to 15 minutes to calm the swelling.

How to Drain a Mastitis Teat in a Dog

If your veterinarian approves, you can drain a teat by gently squeezing it to empty the excess milk. You can also combine this with using a warm compress to help the milk flower better.

Preventing Mastitis

Spaying your dog can be a very effective way of preventing mastitis, although a spayed dog can develop the condition. If spaying is not an option, practicing proper hygiene to prevent mastitis in your whelping dog can help to prevent the condition. You should regularly clean and change the bedding for your dog and her puppies. Check her teats often and clean them gently after feeding times and after any time she goes out to eliminate. Examine her teats often for nicks and cuts from puppy nails and be sure to trim the puppies' nails often as well. Shaving the hair around the nipple area may also help prevent infection.


With proper treatment, it is possible for a female to recover and go on to rear other litters. However, a dog is more susceptible to future mastitis infections once she has had one, and spaying may become necessary at some point.

A Dangerous Condition

A bout of canine mastitis can have a devastating impact on a dog and her litter if it isn't spotted in time. Now that you know the telltale signs to watch for, you'll be better prepared to deal with the situation if it ever arises.

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Canine Mastitis