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Mastitis in dogs is an infection of the mammary glands. It typically affects nursing female dogs, but it can also occur after a false pregnancy. It’s typically caused by a bacterial infection.

Mastitis in dogs is not common, but it can be potentially life-threatening if it’s left untreated. It’s imperative to treat mastitis as quickly as possible, which is why you need to be aware of the symptoms of mastitis in dogs so that you can catch it early on.

In this blog post, we’ll explore what mastitis is, the symptoms of mastitis in dogs, how to treat mastitis in dogs, and more. If your dog is pregnant or recently gave birth, it’s important to read up on mastitis, so you can quickly identify the symptoms and get your dog the proper treatment.

What Is Mastitis in Dogs?

Mastitis is a term that’s used to describe an inflammation of the mammary glands in dogs. Mastitis usually occurs from a bacterial infection, but it can happen from a fungal infection as well. It usually occurs in female dogs who are nursing a new litter of puppies, but it can happen to dogs who aren’t pregnant or nursing1.

Female golden retriever nursing puppies

When the mammary glands get infected due to mastitis, they will swell and become very painful for the dog. If a dog has mastitis, nursing puppies should not drink from the affected teats, as the milk will be toxic for them to consume.

Mastitis can occur in a single gland or within multiple glands. Poor sanitary conditions, trauma caused by offspring, and systemic infection can make a dog more likely to develop mastitis. 

Mastitis can be acute, meaning it appears suddenly and lasts for a short period of time, or chronic, meaning it lasts for a long period and gets worse over time. The condition can quickly progress from a mild infection in one gland to an abscess in the gland or even a fatal systemic illness1. Because of this, it’s crucial to bring your dog to the vet as soon as you notice any symptoms of mastitis. The quicker your dog gets treated, the better recovery they’ll have.

What Are Symptoms of Mastitis in Dogs?

The symptoms of mastitis in dogs will vary depending on the severity of the condition and how early on it is. For example, in mild cases, the first noticeable sign of mastitis is usually that the nursing puppies will not be gaining weight as quickly as they should be. In this case, the mother will likely not show any signs of mastitis and might just be experiencing mild discomfort.

However, mastitis in dogs can quickly progress and turn into more obvious and detrimental symptoms, which is why it’s important to keep a close eye on your dog if they’re nursing. Some other symptoms of mastitis in dogs that you should look out for include1:

Symptoms of mastitis in dogs

  • Depression or dog lethargy
  • Decreased appetite
  • Anorexia
  • Fever
  • Dehydration
  • Reluctance to nurse puppies or discomfort when nursing
  • Puppies are failing to thrive
  • Hot, firm, and swollen breast tissue
  • Teats are bruised or purplish-blue
  • Milk from affected glands appears thin, cream-colored, watery, or bloody
  • Abscess on the affected glands

As the disease worsens, a dog with mastitis will become more visibly ill. Affected dogs may also develop signs of septic shock, including shaking, weakness, panting, and low blood pressure. You may even notice your dog vomiting as the infection begins to enter their bloodstream. To prevent this from happening, bring your dog to the vet as soon as you notice the initial signs of swelling in the mammary glands and failure of the puppies to thrive. 

What Causes Mastitis in Dogs?

Mastitis in dogs is typically caused by a bacterial infection. The most common bacteria that will cause this infection are Escherichia coli (E. coli), Staphylococci, and β-hemolytic Streptococci1. There are a couple of ways that bacteria can access the mammary glands, such as:

  • An infection up the teat canal from the skin
  • Trauma to the nipple, teat canal, or mammary glands caused by puppies’ nursing
  • Poor sanitary conditions
  • The spread of a system infection that’s occurring elsewhere in the body
  • Extended periods of time of milk accumulation in the mammary glands without removal
    • This can result from sudden weaning of puppies

There is a chance that mastitis occurs in a dog even if they aren’t pregnant or nursing. In this case, it may be caused by cancer of the mammary glands, which would require immediate medical attention from a vet.

How Is Mastitis in Dogs Diagnosed?

If you notice any of the above symptoms of mastitis in your dog, you should bring them to the vet immediately. For a vet to make a proper diagnosis, they will need to conduct a thorough physical exam. They may also run a few laboratory tests to confirm the diagnosis and rule out other conditions.

The physical examination will indicate if your dog is suffering from galactostasis, which is a milk engorgement of the glands without an infection, or mastitis, which is when an infection is present. The severity of symptoms will also help a vet identify which one they’re suffering from.

Some of the laboratory tests that a vet may perform include2:

How mastitis in dogs can be diagnosed

  • Blood cell count: A blood cell count test will assess the levels of red blood cells, white blood cells, and platelets in your dog’s blood. Any changes in the white blood cell count can help a vet determine the severity of the infection.
  • Bacterial culture: A bacterial culture will be performed if a bacterial infection is present or if the infection isn’t responding well to an antibiotic. In a bacterial culture, milk will be collected from the mammary glands and sent to a lab so that the bacteria can be further examined. Antibiotic sensitivity testing will then be done to figure out the best antibiotic for treatment.
  • Milk cytology: In a milk cytology, a small amount of milk will be taken from the affected mammary gland and examined under a microscope. If white blood cells or bacteria are present, then a diagnosis of mastitis will be confirmed.

How to Treat Mastitis in Dogs

Mastitis is a serious condition that can be life-threatening if it’s left untreated. Fortunately, most dogs can be treated for mastitis as long as it’s caught early on. There are a few options for mastitis in dogs treatment, but treatment will vary depending on the examination and test results. A combination of treatment methods will most likely be recommended.

How to treat mastitis in dogs

Antibiotic medication will typically be required to treat the bacterial infection, but the type of medication will depend on what bacteria is involved. Pain medication may also be prescribed depending on how severe the symptoms are.

Most dogs with mild mastitis can be treated at home. This is ideal so that the mother can stay close to her puppies as she recovers. If this infection is mild, the puppies may be able to continue nursing, but your vet may recommend hand-milking the affected gland to alleviate discomfort, clear the infection, and promote healing. Hand-milking should be done every six hours2

If the puppies do continue to nurse, it’s imperative to watch them closely for any changes in their consumption, energy, or stool. It’s also possible for the mother to transmit the antibiotic they’re taking to their puppies through nursing, so you need to be very cautious when choosing an antibiotic so that it won’t harm the puppies. 

You can also apply a warm compress or cabbage leaves on your dog’s mammary glands to reduce pain and inflammation. It’s also important to make sure your dog stays well hydrated as they recover2.

In severe cases of mastitis, a dog may need to be hospitalized if intravenous fluid therapy and injectable medications are needed. If the mammary glands are severely infected, a vet may recommend surgery to remove the glands before they worsen. This is why it’s so important to treat mastitis in dogs early on so that it doesn’t get a chance to progress and seriously impact your dog.

To prevent your dog from getting mastitis, there are a few things you should do, such as:

  • Keep a nursing dog’s environment clean
  • Make sure that all of the mammary glands are being used for nursing
  • Trim the puppies’ nails so they won’t damage the mother’s skin
  • Keep the mother’s skin clean

Final Notes

Fortunately, most cases of mastitis in dogs have a good prognosis. With proper treatment, symptoms will resolve within a few weeks, and your dog will be back to its normal, healthy self before you know it.

But still, seeing your dog uncomfortable and in pain can be both heartbreaking and terrifying. But having a good vet to turn to can alleviate a lot of this distress, and you can find a great vet right here at

Dutch connects pet parents with licensed veterinarians who can diagnose and treat a myriad of pet health conditions, whether that be mastitis in dogs or hot spots in dogs. Whatever your dog may be dealing with, we’re here to help you get them the care they need, as soon as you need it.

We work with a network of highly trained and knowledgeable vets who can help with everything from identifying signs of anxiety in dogs to understanding dog body language. Our vets are available with a simple click of a button and ready to help you through any situation you may be going through, no matter how scary it may seem.

Our telemedicine for pets allows pet owners to contact their vets remotely, so they can easily ask questions regarding their pet’s diagnosis and treatment. Telemedicine is a quick and efficient way for pet owners to get connected with licensed vets, without having to physically bring their pet to get seen.

If you’re interested in getting started with Dutch, all you have to do is sign up online, fill out a questionnaire, and you’ll be connected with one of our vets, who will determine if you’re a good match for the program. If you are, you’ll then explain your pet’s situation in more detail and be prescribed any necessary treatment or medication. And with Dutch, you don’t have to worry about physically getting your pet’s prescription filled. We’ll deliver the prescription directly to you in just 7 days. It’s as simple as that.

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  1. Memon, Mushtaq A. "Mastitis in Small Animals." Merck Veterinary Manual.

  2. Lunchick, Paisley. “Mastitis in Nursing Mother Dogs.” American Kennel Club.

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