# Mastitis in Cats: Symptoms, Causes, and Warning Signs Mastitis in cats symptoms usually start with one or more mammary glands that feel swollen, hot, and painful, often with a fever and a cat who refuses to nurse or eat. The condition is an infection of the milk-producing tissue, and it can move fast in nursing mothers. Recognizing it early gives your cat the best chance at a full recovery. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - A swollen, warm, firm, or discolored mammary gland is the most common first sign. - Fever, appetite loss, and hiding often appear before you notice anything wrong with the gland itself. - Discharge from the nipple may look bloody, brown, yellow, or pus-like. - Mastitis is most common in cats who are nursing kittens, but it can also follow trauma or a bite wound near the belly. - Any cat with a fever plus a painful mammary gland needs to be seen the same day, and a cat who is limp, vomiting, or not nursing kittens needs emergency care. ## What Mastitis Looks Like and What Is Normal A normal mammary gland in a nursing cat is soft, pliable, and slightly enlarged. Milk flows easily when kittens nurse, and the gland does not feel hotter than the surrounding skin. After weaning, the glands shrink back down over a few weeks. An infected gland changes in obvious ways. It may feel hard, lumpy, or tight. The skin over it can look red, purple, or dark. When you touch it, your cat may pull away, cry, or try to bite. Some cats guard the belly and refuse to let kittens near it. The discharge is often the giveaway. Normal milk is white or cream colored and thin. Milk from an infected gland may be watery, thick, clotted, or tinged with blood or pus. It can also smell bad. If you see any of these changes, treat it as a sign of infection until your veterinarian says otherwise. Fever is common with feline mastitis. A cat with a mammary gland infection often runs a temperature and acts dull. She may stop eating, hide under the bed, or ignore her kittens. In one reported case, a cat with severe mastitis had a chronic draining wound and a mass in the groin area that had been present for months before the correct diagnosis was made [1]. ## Mastitis in Cats Causes: Why Glands Get Infected Bacteria are the usual culprits. They enter through the nipple opening or through a break in the skin. Once inside, they multiply in the warm, nutrient-rich milk tissue. Staphylococcus species are a well-known cause of mammary infections in cats, and some strains are resistant to common antibiotics [2]. Streptococcus species also cause mastitis in animals, and resistance to some antibiotics has been documented in these bacteria [3]. Other organisms, including mycobacteria, have been found in feline mammary tissue, though these are rare [1]. ### Common Causes and How Urgent They Are | Cause | Typical clues | How urgent | |---|---|---| | Nursing and milk stasis | Recent birth, engorged glands, kittens not nursing evenly | Same-day vet visit | | Bacterial infection (Staphylococcus, Streptococcus) | Hot, painful gland, fever, pus-like milk | Same-day vet visit | | Bite wound or trauma near the belly | Visible wound, swelling, history of a fight | Same-day vet visit | | Mycobacterial infection | Long-standing draining wound or mass that does not heal | Prompt vet visit, may need surgery and long treatment | | Unknown or mixed infection | Signs that do not fit one pattern | Same-day vet visit with testing | Nursing is the biggest risk factor. Kittens may scratch the gland with tiny claws, or a gland may not drain fully if a kitten is weak or the litter is small. Milk that sits in the gland is a perfect place for bacteria to grow. Trauma is the second big cause. A bite from another cat near the belly can seed bacteria deep into the tissue. In the reported mycobacterial case, the problem began with a bite wound on the thigh and a mass in the groin, and the infection was not a tumor at all [1]. If your cat has other signs of infection or pain, such as head shaking or scratching at the ears, our guide to [ear infections in cats symptoms](/knowledge/veterinary-medicine/symptom-guides/ear-infections-in-cats-symptoms) can help you sort out what you are seeing. Cats with a fever and poor appetite may also show signs covered in our article on [upper respiratory infection in cats symptoms](/knowledge/veterinary-medicine/symptom-guides/upper-respiratory-infection-in-cats-symptoms). ## Red Flags That Mean an Emergency Some signs mean you should stop reading and call an emergency clinic now. - Your cat is limp, unresponsive, or too weak to stand. - She is vomiting, breathing fast, or has pale or muddy gums. - The gland is black, peeling, or draining large amounts of pus. - She has a high fever and will not eat or drink at all. - She is a nursing mother who has stopped caring for her kittens. These signs can point to sepsis, a body-wide infection that needs treatment right away. Do not wait for a morning appointment. Call your veterinarian the same day if you see any of these: - A swollen, hot, or painful mammary gland. - Fever, even a mild one. - Discolored or foul-smelling milk. - A cat who cries when kittens try to nurse. - A wound or lump near the belly that is not healing. ## Safe Things You Can Do at Home While You Wait You cannot cure mastitis at home, but you can keep your cat comfortable and avoid making things worse. - Do not squeeze or massage the gland. Pressure can push bacteria deeper and cause more pain. - Do not give human pain relievers. Many are toxic to cats, and the dose depends on your cat's weight and health. Your veterinarian will choose a safe drug and calculate the dose for your pet. - Keep the area clean and dry. A warm, damp cloth held gently against the skin for a few minutes may ease discomfort, but stop if your cat objects. - Separate the kittens if the gland is infected. They should not drink milk from an infected gland. Ask your veterinarian what to feed them in the meantime. - Offer water and small, tempting meals. A cat with a fever often will not eat much, and hydration matters. - Take a photo of the gland and note the time you first saw changes. This helps your veterinarian track how fast things are moving. If your cat is straining to urinate or has blood in her urine, that is a different problem. Our article on [what are symptoms of a uti in a cat](/knowledge/veterinary-medicine/symptom-guides/what-are-symptoms-of-a-uti-in-a-cat) explains those signs. ## What Your Veterinarian Will Check and Test Your veterinarian will start with a full physical exam. They will check your cat's temperature, heart rate, and hydration. They will feel every mammary gland, not just the one that looks wrong, because infection can spread. Next comes milk sampling. Your veterinarian may collect a small amount of milk or discharge from the gland and send it to a lab. A sample can be cultured to identify the exact bacteria involved. This matters because different bacteria need different antibiotics, and resistance is a real problem in feline staphylococcal infections [2]. In animals with mastitis, identifying the pathogen is the key to choosing a treatment that works [4]. Blood work is common. A complete blood count and chemistry panel show how the body is responding to infection and whether organs like the kidneys and liver are affected. Imaging may be needed. An ultrasound can show whether the gland contains fluid pockets or abscesses that need to be drained. X-rays can help if your veterinarian suspects a mass or a foreign body. Treatment usually includes antibiotics, pain control, and supportive care. Your veterinarian will pick the antibiotic based on culture results when possible. Some infections need long courses of treatment. In the reported mycobacterial case, the cat needed 24 weeks of combined therapy before reaching full remission [1]. Your veterinarian sets the dose and duration for your cat based on weight, kidney and liver health, and how the infection responds. If the gland is abscessed, it may need to be lanced and flushed. In severe cases, surgery to remove damaged tissue may be needed. Most cats with simple mastitis respond well to antibiotics and home care. ## Prevention and Monitoring You cannot prevent every case, but you can lower the risk. - Check mammary glands daily during nursing. Feel each gland gently. Look for redness, heat, or firm spots. - Keep the nursing area clean. Wash bedding often and keep the nest dry. - Trim kitten nails. Tiny claws cause small scratches that let bacteria in. - Watch for uneven nursing. If one gland stays full while others empty, a kitten may be missing it. - Treat wounds near the belly right away. A bite or scratch near a gland should be seen by a vet. - Spay your cat if she is not part of a breeding program. Spaying removes the mammary tissue's hormone stimulation and prevents future pregnancies and nursing cycles. After treatment, recheck with your veterinarian as scheduled. Some infections come back if antibiotics are stopped too early. Watch for the same signs you saw the first time: swelling, heat, pain, fever, or bad milk. ## Limitations and When to Contact a Veterinarian Mastitis in cats can look mild at the start and become serious within a day. There is no home test that tells you whether the infection is spreading. Call your veterinarian the same day if you notice a swollen, hot, or painful mammary gland, a fever, or discolored milk. Go to an emergency clinic now if your cat is weak, vomiting, breathing fast, has black or peeling skin on the gland, or has stopped caring for her kittens. Routine visits are fine for a cat who has finished treatment and needs a recheck, or for a cat with a small lump that has not changed. Every case is different, and only your veterinarian can examine your cat, run the right tests, and set a treatment plan for her. ## Frequently Asked Questions ### Can mastitis in cats go away on its own? Mild cases sometimes improve with supportive care, but most need antibiotics. Waiting too long lets the infection spread and makes treatment harder. Call your veterinarian as soon as you see a swollen or painful gland. ### Is mastitis contagious to other cats or to people? The bacteria involved can pass between animals in some situations, and some staphylococcal strains found in cats are resistant to common antibiotics [2]. Wash your hands after handling the gland or soiled bedding. Keep the infected cat away from other nursing mothers. ### Can a cat with mastitis still nurse her kittens? Kittens should not drink from an infected gland. Your veterinarian will tell you whether the other glands are safe and what to feed the kittens in the meantime. Hand-feeding or a foster mother may be needed. ### How long does mastitis treatment take in cats? It depends on the cause and how deep the infection goes. Simple bacterial cases often improve within days of starting antibiotics, but the full course must be finished. Some infections, including mycobacterial ones, can take months of treatment [1]. ### What does mastitis discharge look like in cats? It can be watery, thick, clotted, bloody, brown, yellow, or pus-like, and it may smell bad. Normal milk is thin and white or cream colored. Any change in color, texture, or smell is a reason to call your veterinarian. ## Related Articles - [Ear Infections In Cats Symptoms](/knowledge/veterinary-medicine/symptom-guides/ear-infections-in-cats-symptoms) - [Upper Respiratory Infection In Cats Symptoms](/knowledge/veterinary-medicine/symptom-guides/upper-respiratory-infection-in-cats-symptoms) - [Ear Infection Cats Symptoms](/knowledge/veterinary-medicine/symptom-guides/ear-infection-cats-symptoms) - [Symptoms Of Cat Ear Infection](/knowledge/veterinary-medicine/symptom-guides/symptoms-of-cat-ear-infection) - [What Are Symptoms Of A Uti In A Cat](/knowledge/veterinary-medicine/symptom-guides/what-are-symptoms-of-a-uti-in-a-cat) - [Symptoms Of Urinary Tract Infection In A Cat](/knowledge/veterinary-medicine/symptom-guides/cat-urinary-tract-infection-symptom) - [Mastitis in Cats: Home Treatment and Vet Care](/knowledge/veterinary-medicine/vet-visit-decisions/mastitis-cats-home-treatment) - [Mastitis in Cats Not Pregnant: Causes and Next Steps](/knowledge/veterinary-medicine/symptom-guides/mastitis-cats-not-pregnant) - [Mastitis in Cats: Antibiotics and Treatment Options](/knowledge/veterinary-medicine/pet-medication-guide/mastitis-cats-antibiotics-treatment) ## References 1. [Feline Cutaneous Mycobacteriosis Caused by Mycobacterium farcinogenes: The First Case Report from Asia](https://pubmed.ncbi.nlm.nih.gov/42738521/). Animals : an open access journal from MDPI, 2026. 2. [Emerging threats and zoonotic implications of antibiotic-resistant Staphylococcus spp. in domesticated cats: a review](https://pubmed.ncbi.nlm.nih.gov/42332304/). Antonie van Leeuwenhoek, 2026. 3. [Subclinical Mastitis Related to Streptococcus canis Infection in Dairy Cattle](https://pubmed.ncbi.nlm.nih.gov/40266987/). Veterinary sciences, 2025. 4. [A Rapid and Inexpensive PCR Test for Mastitis Diagnosis Based on NGS Data](https://pubmed.ncbi.nlm.nih.gov/38787275/). Pathogens (Basel, Switzerland), 2024. ## Further Reading - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)