Mastitis in Cats

Updated Sep. 12, 2023

In This Article


What Is Mastitis in Cats?

Mastitis is an inflammation or swelling of a mammary gland, and is a condition usually linked to a bacterial infection. Mastitis can affect just one mammary gland, but female cats typically have eight of them and more than one can be involved.

Mastitis isn’t all that common in cats, but when it does occur, it’s most often seen in female cats who are nursing kittens or who have just stopped. Without treatment, cats with mastitis can become very sick and even die, but thankfully, most respond well to the correct antibiotics and recover quickly.

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Symptoms of Mastitis in Cats

When mammary glands are inflamed, they may be:

  • Warm to the touch

  • Red

  • Swollen

  • Firmer than normal

  • Painful

The milk that comes out of the nipple can be unusually thick and contain visible blood or pus. In severe cases, the skin over the gland may become dark and ulcerated (having an open sore). If an infection has led to an abscess (a pocket of pus), it can burst, and you may notice drainage of blood and pus from a wound on the skin.

At first, cats with mastitis may not seem to feel sick, but systemic signs of infection often develop with time. These may include:

  • Fever

  • Lethargy

  • Poor appetite

  • Vomiting

Because mastitis is painful, cats may not want to nurse, which can lead to poor weight gain in their kittens.

Causes of Mastitis in Cats

Most cases of mastitis develop after bacteria in the environment make their way up the teat canal, causing an infection in the mammary gland. Certain situations make this more likely, including:

  • Damp and dirty surroundings—The more bacteria that are present in a cat’s surroundings, the greater the chances of infection. Keeping a nursing cat’s environment clean and dry can help prevent mastitis.

  • Trauma—Tissue damage to a teat or other parts of a mammary gland can give bacteria a way into deeper tissues.

  • Milk collecting in the mammary glands—The normal flow of milk through and out of a mammary gland removes bacteria and helps prevent infection. Milk can back up in mammary glands (a condition called galactostasis) when a litter of kittens stops nursing abruptly or because of anatomic abnormalities.

  • Mammary hyperplasia—This is a condition that may be confused with or lead to mastitis. After a cat ovulates (whether she becomes pregnant or not), her ovaries produce progesterone. Sometimes, this leads to her mammary glands becoming unusually large. The skin over them can become damaged, which may lead to infection.

  • Mammary cancer—Infections can develop in and around tumors when a cat has mammary cancer.

How Veterinarians Diagnose Mastitis in Cats

A veterinarian can usually diagnose mastitis based on finding signs of infection in one or more mammary glands in a cat who is or has recently been nursing kittens. The veterinarian may look at a sample of milk under the microscope to confirm infection.

However, it’s important to know what bacteria are involved and which antibiotics are most likely to be effective. A culture and sensitivity test done on a milk sample will usually provide this information. It may also be necessary to run bloodwork to see how severely affected a cat is and do tissue biopsies to rule out other conditions.

Antibiotics for treatment are only available by prescription, so a veterinary visit is needed. But pet parents are often taking care of a mother and a whole litter of kittens. Should you separate them or bring them all to the clinic together? The answer depends on a variety of factors, including how sick the mother is, the age of the kittens, how long they would be kept apart, and how difficult transportation will be.

Ask your veterinarian what you should do when you are making your appointment. And while you’re at it, see if they’d be willing to make a house call or refer you to another veterinarian who could. This is the perfect situation for the doctor to come to the patient.

Treatment for Mastitis in Cats

A veterinarian will first pick an antibiotic that is likely to work well based on the specifics of a cat’s case, but they may make a change when results of the culture and sensitivity test are available.

Commonly prescribed antibiotics for mastitis include:

Pain relief (buprenorphine, for example) and supportive care may also be needed. Surgery to remove severely damaged tissues (due to a large, ruptured abscess, for example) is also sometimes necessary.

One question that often comes up is whether to let kittens continue nursing after their mom has been diagnosed with mastitis. If they are ready to be weaned, it may be easiest to go ahead and do it now. If not, nursing will keep the milk flowing and can help get bacteria out of the mammary glands. But this is only an option if the mother isn’t too severely affected, will allow the kittens to nurse, and can be put on medications that are safe for the kittens too.

Recovery and Management for Mastitis in Cats

Unless the cat needs surgery or is very sick, they can usually be treated for mastitis at home. Your veterinarian will go over how to give your cat the medications they have prescribed and any other treatments they recommend. Applying warm or cool compresses (or cabbage leaves) can help relieve swelling and discomfort.

In most cases, cats with mastitis will need to be given antibiotics for two to three weeks, but their condition should start improving within just a few days of starting treatment. Call your veterinarian for advice if there’s no improvement or if your cat’s condition gets worse at any time.

Once your cat has recovered, it’s time to consider having her spayed. Spaying is the best form of prevention, since most cases of mastitis in cats are connected to lactation (nursing).

Mastitis in Cats

Why does my spayed cat have swollen nipples?

The nipples of spayed cats are usually small and don’t change much from day to day or month to month. A veterinary examination is needed if a spayed cat’s nipples become swollen. Possible causes include a piece of an ovary being left behind during a spay, hormone exposure through medications, tumors that produce hormones, or mammary cancer.

Why is my cat’s nipple bleeding?

Bleeding from a nipple can be a sign of trauma, mastitis, mammary cancer, or other potentially serious health problems. Unless the problem is minor and easily managed at home (a small abrasion or scrape, for example), a cat with a bleeding nipple should be seen by a veterinarian.

Featured Image: Dolmatov


Abramowitz C, Deutch A, Shamsian E, Musheyev Y, Ftiha F, Burnstein S. Red Cabbage: A Novel Treatment for Periductal Lactational Mastitis. Cureus. 2022;14(12):e33191.


Jennifer Coates, DVM


Jennifer Coates, DVM


Dr. Jennifer Coates is an accomplished veterinarian, writer, editor, and consultant with years of experience in the fields of veterinary...

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