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Mastitis in Dogs — Causes, Symptoms & Treatments

↯ Key takeaway points

  • Canine mastitis is when one or more mammary glands become infected with bacteria, which can be caused by injury, poor hygiene or a weakened immune system.
  • Symptoms of mastitis in dogs include rejected puppies, visibly swollen and discolored mammary glands, lethargy, low energy and pain.
  • Treatment includes taking antibiotics or undergoing surgery, and sometimes IV fluid therapy.
  • Breeders and owners can prevent recurrence of the condition by keeping the dam and her surroundings clean and hygienic, regularly checking the nipples for signs of injury, and keeping puppies' nails trimmed.
  • Puppies should not nurse from a female dog with mastitis, and dog breeders can bottle-feed the litter during treatment.
Breeding Business is passionate about all sorts of domesticated pets. They have written dozens of articles across the web.
Zoo and wildlife doctor in veterinary medicine passionate about animal welfare and preventive medicine.
Published on
Saturday 6 October 2018
Last updated on
Thursday 22 June 2023
Mastitis in Dogs
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Canine mastitis is a condition where one or more of a dog’s mammary glands become infected with bacteria. It’s important to catch it early because it can be treated with antibiotics as an outpatient. However, if the condition is not caught early, the dog may require hospitalization with IV therapy or even surgery.

Mastitis is more common in pregnant female dogs, especially those with more puppies than teats. This is because the puppies put a lot of stress on their mother’s mammary glands over several weeks. If the area is not kept clean or if there are scratches or cracks, it can quickly become infected.

To ensure a quick recovery, dog breeders should check their female’s teats daily. Catching mastitis early can prevent a lot of pain and problems for both the dog and the owner. If you notice any signs of mastitis, it’s important to contact your vet right away

What is Mastitis in Dogs?

Mastitis is a condition that can occur in lactating female dogs when one or more of their mammary glands becomes infected with bacteria. The most common bacteria associated with mastitis in dogs are E. coli, Streptococci, and Staphylococcus. It’s typically not a concern for dogs who are not nursing, such as those experiencing a pseudopregnancy.

There are two types of canine mastitis to be aware of:

  • Galactostasis, which tends to occur in the later stages of pregnancy and is marked by caked breasts
  • Acute septic mastitis, which is more serious and occurs when the bacteria have made its way into the mammary gland, causing an abscess.

If left untreated, mastitis can result in a malignant or benign condition, which is why it’s important to have a thorough examination of the mother’s milk as soon as possible. It’s a potentially life-threatening condition, so it should always be taken seriously and handled with care.

It’s important to note that canine mastitis is not cancer and should not be confused with mast cell tumors or Mastocytoma, which are cancerous tumors located on the skin. If you suspect your dog has mastitis, seek veterinary care right away.

What Causes Mastitis in Dogs?

During the whelping phase, a female dog is exposed to several stressors in her life. The stress of pregnancy, followed by nursing and dealing with the sharp teeth of her young, creates an environment where bacteria can thrive. Under normal circumstances, the mother’s immune system can fight off these bacteria. However, if the mother is not provided with proper nutrition or a clean environment, her immune system may not function at its optimal level.

As a result of the pain caused by canine mastitis, a female dog may reject her puppies and avoid nursing altogether.

In summary, a female dog’s body goes through a lot during the whelping phase, and the stressors and lack of proper nutrition or sanitary conditions can lead to the development of canine mastitis. This condition can cause significant pain, leading to the mother rejecting her puppies and refusing to nurse them. Therefore, it’s important to provide the mother with proper care and nutrition to prevent and treat canine mastitis.

[pullquote-right]As a consequence of the pain, a female dog victim of canine mastitis will often reject her puppies and avoid nursing all together.[/pullquote-right]

Ascending infection via a teat

One of the most common causes of canine mastitis is when bacteria enters the teat canal through trauma or injury in one of the nipples. As the bacteria travels up the mammary gland, it can cause an infection. Additionally, certain living conditions can cause bacteria to ascend, due to various irritants present in the dog’s living space.

In summary, trauma or injury in one of the nipples can allow bacteria to enter the teat canal, causing an infection that can travel up the mammary gland. It’s essential to provide a clean living environment for the dog to prevent the ascent of bacteria.

Wounds and scratches on the nipples

During pregnancy, a female dog produces milk in the milk ducts of her mammary glands to nourish her pups. However, puppies can become overexcited and aggressive while nursing, which can lead to scratches on the mother’s nipples. Additionally, nipples can become cracked due to irritation, providing a potential entry point for bacteria to cause an infection in the milk ducts.

In summary, scratches and wounds on the nipples can occur when puppies become overexcited while nursing. These scratches and cracks can provide a breeding ground for bacteria to cause an infection in the milk ducts. It’s essential to monitor and address any damage to the nipples to prevent the development of mastitis.

Poor hygiene

Poor hygiene can lead to bacterial infections in a dog’s mammary glands. If the mother dog’s living environment is not clean, it can harbor harmful bacteria that can cause mastitis. Additionally, the area around the nipples can also be a breeding ground for germs. To prevent this, it is important to maintain proper hygiene by regularly cleaning the mother dog, her breasts, and the surrounding area where she and her puppies live.

Other Causes

Other common causes of Mastitis include systematic infections that originate elsewhere in the body and make their way to the teat. Milk accumulation in the mammary duct due to prolonged periods of the milk production may increase the chances of bacteria buildup and lead to inflammation. In more serious cases, Mastitis can be a symptom of mammary gland cancer. Because of this, it’s vitally important to get the dam checked as soon as possible as it is not always possible to know what stage of Mastitis she is in or whether the infection is caused by more malignant factors.


Dog owners often notice a change in behavior and appearance in a dam infected by canine mastitis. This change is quite evident in the way she cooperates with her offspring and will most likely alarm her breeder, as long as you are paying attention and monitor the situation regularly.

symptoms of mastitis in dogs
Monitor your female dog to notice a change in behavior and appearance caused by canine mastitis.

Rejecting puppies and less frequent nursing

Due to pain in the infected area of the mammary gland, a dam will begin to reject her puppies and avoid nursing altogether. This is to counteract the extreme discomfort caused by the constant suckling of the pups that further irritates the painful sensation.

As her condition worsens, it may seem she has lost complete interest in her pups and reject any notion to continue the whelping phase. The whelps will cry a lot. While some caretakers may not consider it to be a great deal, this lack of attention is often a sign that indicates something is wrong and she should be checked out.

Visibly swollen and purulent mammary glands

The most prominent signs of a bacterial infection of the breast in dogs are the visible changes noticeable on the teats of the dam. The infected mammary gland will tend to swell up and become distinctly inflamed, swollen, and will begin to show colors of a purulent teat. The infected site will turn red or purple depending on the stage of the advancement and will become more painful.

Often times, after the infection has progressed, the gland may show ulcerative signs and become purulent in which it produces pus-like liquids or blood and show open, visible wounds. Any milk that is expressed from the infected site will produce a more cloudy milk or thicker in composition. Blood and pus may also be found in the extracted milk as well.

Lethargy and overall low energy

A dam that has been infected with the Mastitis infection will show signs of extreme lethargy and fatigue. She will exhibit an overall low energy. She may suffer a loss of appetite, especially when the infection has progressed into inflicting a lot of pain for the mum. These are obvious signs to look for in your bitch that indicate something is definitely wrong and she needs to get checked out. Another sign includes excessive sleep. This is very important to watch out for because these types of infections can spread rather quickly in the body and affect the dam’s overall energy and function.

Other Symptoms

Aside from the most common signs mentioned above, other symptoms to watch out for include lumpy teats that are painful to touch. They may also be very warm or hot when touched. In addition to not wanting to nurse, an infection of the mammary glands may cause the bitch to snap and growl at her puppies. She will exhibit signs of restlessness in the earlier stages before becoming too weak. Some dogs may cry and whimper.


After examining your dog for signs of mastitis, the vet may require laboratory tests to confirm the diagnosis and rule out other diseases. It’s important to give the vet a detailed history of your dog’s health and any events leading up to the current symptoms.

The lab tests will include a complete blood count analysis, which will check the number of white and red blood cells and platelets present in your dog’s blood. Additionally, a milk cytology test may be conducted, where droplets of milk are examined under a microscope to detect white blood cell counts or bacteria.

If the mastitis is not responding to antibiotic treatment, a bacterial culture test may be necessary. In this test, milk is extracted from the infected site and the bacterium is isolated for further testing.


Canine mastitis in dogs may be treated with a course of antibiotics, an intravenous fluid therapy, or surgery. The treatment will depend on how early the mastis was detected and diagnosed.


An antibiotic treatment is generally the quickest way to treat and recover from mastitis. They promote an easier recovery while not needing any hospitalization. Treated bitches are able to stay in the comfort of their own home.

In fact, most cases of mastitis in dogs end up with outpatient treatments unless the infection is progressed. That’s why it’s important to get the dog treated right away. During this at-home treatment phase, dogs will normally be prescribed pain medications with oral antibiotics. Antibiotics may pose a threat to nursing puppies, however, as it is possible they can be passed through the mother’s milk.

Intravenous fluid therapy

If the dog’s mastitis infection is severe, the dog needs to be hospitalized. During this process, the bitch will be treated with intravenous fluid therapy as well as injectable medications to keep her stable. Fluid therapy is also needed for dogs who are having difficulties with weight management, for example. This fluid therapy will help keep her at an even weight and provide the necessary nutrients she needs for healing during the treatment.

In some worst cases, the surgical removal of the infected glands may be required.

Milking out the affected mammary glands to keep tracts clean

For less serious infections, breeders and dog owners may manually milk the duct by hand. The hand-milking movement will alleviate pressure from the infected teat and helps to increase the blood flow. This will greatly improve the dam’s condition and encourage healing. The milking should be done every six hours for optimum results.

Although dog breeders have the option of manually assisting in the treatment of mastitis, this should be recommended by your veterinarian rather than your own opinion. This is then done on an outpatient basis, meaning the bitch does not require hospitalized.

Can puppies nurse from a female with mastitis?

In most cases, it is best not to allow puppies to continue nursing after the bitch is diagnosed with canine mastitis in one of her mammary glands. In the early stages, puppies may be more adequately fit to extract milk from the glands as opposed to hand-milking but there will always be the concern of whether the antibiotics used in the treatment may pass over to the puppies. Additionally, the bitch may, in fact, be too sore to allow nursing to continue.


Having said that, dog breeders will be forced to take nursing matters into their own hands by bottle-feeding the litter. In these cases, buy some high-quality puppy formula replacement and get the puppies on a regular feeding schedule just as they would while they were nursing. Buy a bottle and feed them accordingly. This should be done until the mammary glands are all sound and clear from any infection.

Prevention and Avoiding Recurrence

Canine mastitis is a dangerous condition that can harm dogs if not treated on time. If a female dog has had mastitis in the past, it’s more likely to happen again. Therefore, prevention is essential. It’s recommended to avoid breeding females who have experienced mastitis.

Fortunately, there are several steps you can take to minimize or prevent mastitis. Hygiene is critical. Keep your dog’s surroundings clean, especially in the areas where she spends most of her time. Additionally, you can shave the mammary glands and teats to reduce the risk of infection. Regular cleaning with wet gauze or saltwater is essential, as well as checking the nipples.

Many cases of mastitis occur due to injuries caused by puppies’ teeth and nails during nursing. To prevent this, keep their nails trimmed regularly. Additionally, giving your dog a weekly salt bath while nursing can be helpful. If there are more teats than pups, organize a rotation between feedings to ensure all teats are used.

Early intervention is crucial in preventing the bacterial infection from becoming life-threatening. So if you notice any of the symptoms of mastitis, get your dog checked by a vet as soon as possible.

One comment on “Mastitis in Dogs — Causes, Symptoms & Treatments”

  1. Mable

    How long does it take for pups to wean?

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