- What causes mastitis in dogs
- Mastitis in dogs: symptoms to watch for
- Normal nursing changes vs. mastitis vs. emergency: know the difference
- How vets diagnose and treat mastitis in dogs
- Home care: what actually helps (and what doesn't)
- How to prevent mastitis in dogs
- Does pet insurance cover mastitis in dogs
- Before we go
- Frequently Asked Questions
If one of your nursing dog’s mammary glands (the milk-producing tissue along her belly) looks swollen, red, or feels hot, trust that instinct. Mastitis is a painful infection of those glands, and it can escalate quickly. Caught early, it’s very treatable. Knowing what to look for makes all the difference.
Most cases happen in nursing dogs in the weeks after giving birth, but mastitis can also show up during a false pregnancy, and in rare cases, even in male dogs.
TL;DR
- Mastitis is an inflammation or infection of the mammary glands. It’s most common in nursing dogs, but any dog can get it.
- Early signs: swollen, red, warm, or hard glands, and milk that looks discolored, bloody, or watery. Fever and low appetite are red flags.
- Severe cases can become gangrenous (where the tissue dies) or septic (where infection spreads through the bloodstream). Both are emergencies.
- Treatment almost always means a vet visit and antibiotics. Warm compresses can offer comfort, but they’re not a substitute for medical care.
What causes mastitis in dogs
Mastitis happens when bacteria enter the mammary gland, usually through the nipple. The most common culprit is E. coli, though Staphylococcus and Streptococcus bacteria show up frequently too.
In nursing dogs, bacteria can get in through scratches from puppies’ sharp nails, unsanitary whelping conditions, or milk stasis (also called galactostasis), which is when milk builds up in a gland that isn’t being drained. Stagnant milk creates a warm, nutrient-rich environment where bacteria thrive.
Dogs going through a false pregnancy (where the body behaves as though it’s pregnant even when it isn’t) can also develop mastitis because the mammary glands produce milk with nowhere to go. Male dogs with hormonal imbalances or certain tumors can develop it too, though this is uncommon.
Mastitis in dogs: symptoms to watch for
Early mastitis can be subtle. During the nursing period, check the mammary glands regularly. Here’s what to look for:
- Swollen, firm, or lumpy glands that feel different from normal nursing fullness
- Skin that’s red, warm, or painful when you gently press near the nipple
- Milk that looks yellow, brown, bloody, or watery instead of white
- Your dog pulling away during nursing, or puppies refusing a specific gland
- Fever (above 103°F), low energy, or decreased appetite
- Discharge or pus leaking from the nipple
- Puppies crying more than usual or not gaining weight, which are both signs the milk quality may be affected
Even if only one or two glands look mildly affected, don’t wait. Call your vet.
Normal nursing changes vs. mastitis vs. emergency: know the difference
One of the hardest parts of spotting mastitis is that some changes to a nursing dog’s mammary glands are totally normal. Here’s a side-by-side comparison to help you figure out where your dog falls.
| What you’re seeing | Normal nursing engorgement | Mastitis (infection) | Emergency (gangrenous or septic) |
|---|---|---|---|
| Gland appearance | Full, slightly firm, symmetrical | Swollen, hard, uneven | Dark purple, black, or bluish skin; tissue may look dead |
| Skin temperature | Slightly warm | Hot and painful to touch | Very hot, then cold as tissue dies |
| Milk color | White or slightly yellow (normal colostrum early on) | Yellow, brown, bloody, or watery | Bloody, foul-smelling, or no milk at all |
| Dog’s behavior | Normal, alert, eating well | Reluctant to nurse, may seem sore | Severely lethargic, not eating, possibly collapsing |
| Fever | None | Possible (over 103°F) | High fever or dangerously low temperature |
| What to do | Monitor, keep area clean | Call your vet today | Emergency vet visit now |
Gangrenous mastitis is the worst-case scenario: the mammary tissue begins to die, and infection can spread through the bloodstream (a condition called sepsis). If the skin around a gland looks dark or discolored, or starts to smell, go to an emergency vet immediately.
How vets diagnose and treat mastitis in dogs
Diagnosis
Your vet will examine the mammary glands and may collect a small milk sample to look at under a microscope and send to a lab. This is called a culture and sensitivity test, which identifies which bacteria is causing the infection and which antibiotic will actually work. Blood work may also be run to check whether the infection has spread.
Treatment
For most cases, your vet will prescribe antibiotics and pain relief. The specific antibiotic depends on the culture results, so always follow your vet’s guidance rather than seeking something over the counter.
In mild-to-moderate cases, nursing can usually continue. Puppies draining the affected gland actually helps clear the infection. If the milk is contaminated or your dog is too unwell, your vet will advise whether to temporarily separate the puppies and switch them to supplemental feeding.
For severe cases involving an abscess (a pocket of pus inside the gland) or gangrenous mastitis, surgery may be needed to drain the abscess or remove the affected tissue entirely. It’s less common, but it can significantly affect the cost of treatment.
Home care: what actually helps (and what doesn’t)
There are a few safe, vet-approved things you can do at home alongside treatment:
- Warm compresses: A warm, damp cloth on the affected gland for about 10 minutes, a few times a day, can ease discomfort and encourage milk flow. Always check with your vet first.
- Gentle milking: If puppies aren’t nursing from an affected gland, your vet may show you how to manually express it to prevent further milk buildup.
- Keeping the area clean: Wipe nipples gently after nursing and keep the whelping area sanitary.
- Monitoring puppy weight: Weigh puppies daily to make sure they’re getting enough nutrition during treatment.
A note on cabbage leaves: You may have seen cabbage leaves recommended as a home remedy. This comes from human nursing practice, where they’re sometimes used to ease engorgement. Some veterinary sources do note they can help with pain and inflammation when used alongside prescribed treatment, but they’re not a substitute for antibiotics if there’s a bacterial infection. Use them only with your vet’s guidance, and never in place of medical care.
How to prevent mastitis in dogs
You can’t prevent every case, but these steps lower the risk during the weeks after whelping:
- Keep the whelping area clean and change bedding frequently.
- Trim puppies’ nails regularly so they don’t scratch the skin around the nipples.
- Make sure all mammary glands are being nursed from. A bypassed gland where milk builds up (galactostasis, also called milk stasis) becomes a breeding ground for bacteria.
- Wean gradually. Stopping nursing all at once can cause engorgement and milk stasis.
- Check the mammary glands daily. You’re looking for heat, swelling, hardness, or any change in the milk.
Does pet insurance cover mastitis in dogs
Mastitis treatment can add up quickly, especially if your dog needs hospitalization, IV antibiotics, or surgery. Depending on severity, costs can run into the hundreds or thousands of dollars.
Lemonade pet insurance doesn’t cover conditions related to pregnancy or breeding, so mastitis that develops in a nursing dog after whelping would not be eligible for coverage. That said, if your dog develops mastitis outside of any pregnancy or breeding context (for example, during a false pregnancy or as a non-pregnant adult), it may be covered as long as it isn’t a pre-existing condition. That could include lab work, prescription medications, and surgery if needed.
Before we go
Mastitis is painful, potentially serious, and easy to miss early on. If you’re seeing a swollen or discolored mammary gland, abnormal milk, or a nursing dog who just seems off, call your vet. Most cases resolve well with antibiotics and supportive care, but the window between manageable and emergency can be short. Trust what you’re seeing and act on it.
Frequently Asked Questions
Can mastitis in dogs go away on its own?
Mild engorgement from milk stasis may improve with frequent nursing and warm compresses, but a true bacterial infection won’t resolve without antibiotics. Leaving it untreated risks it turning into an abscess or gangrenous mastitis, which is a medical emergency. Always contact your vet if you suspect infection.
What does mastitis look like in dogs?
An affected mammary gland will typically look swollen, feel hard and hot, and may appear red. The skin might look stretched or shiny. In severe gangrenous cases, the skin can turn purple, grey, or black. Milk from the gland may look yellow, brown, bloody, or watery instead of its normal white color.
Can a dog get mastitis if she’s not pregnant?
Yes. Dogs going through a false pregnancy (pseudopregnancy) can develop mastitis because their mammary glands produce milk even without puppies present. Mastitis in dogs not pregnant is less common but very real, and it’s treated the same way as in nursing dogs.
Can male dogs get mastitis?
Rarely, but yes. Mastitis in male dogs can occur, usually linked to hormonal imbalances or mammary tumors. It’s much less common than in female dogs, but if you notice a swollen, painful area near a male dog’s nipples, have a vet take a look.
Should I separate the puppies from a dog with mastitis?
Not automatically. In most mild-to-moderate cases, continuing to nurse from the affected gland actually helps clear the infection by draining the milk. Your vet will advise on whether separation is needed based on how sick the mother is and whether the milk is safe for the puppies.
A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC. The statements do not apply to policies underwritten by other carriers.
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