Help, her breasts are like balloons!

A practical guide to mastitis and other postpartum complications

After giving birth—or even without having actually been pregnant—some females may develop acute inflammation in their mammary glands. This condition is known as mastitis, and although it starts locally, it can progress rapidly and become a serious systemic condition if not treated in time.

Mastitis can occur in different contexts: during natural lactation, when there is overproduction or poor suckling by the puppies, or in the context of pseudopregnancy, where milk production occurs without puppies to empty the breasts. In both cases, the accumulation of milk and the manipulation of the mammary tissue create a perfect environment for bacterial proliferation.

Clinical signs may include pain, heat, redness, fever, loss of appetite, and refusal to nurse. Often, guardians do not recognise the problem until the inflammation is evident or the pet begins to show general discomfort.

Therefore, detecting mastitis early and knowing the tools for prevention, such as sterilisation, is essential to ensure the physical and emotional health of our furry companions.

What is mastitis, why does it occur, and when does it appear?

After giving birth — or even without having actually been pregnant — some females may develop acute inflammation of the mammary glands. This condition is known as mastitis and, although it often starts as a localised problem, it can quickly develop into a generalised problem if not treated in time. At the population level, mastitis in bitches is considered a rare condition in companion animals, with an estimated incidence of less than 1% in the general population, but studies show that this figure can increase significantly in intensive reproductive contexts, with prevalences of 10–20% reported in breeding bitches and large litters. HERE 1 In a comprehensive survey of breeders with hundreds of registered litters, mastitis was reported in around 9.2% of litters, and it was also noted that a significant percentage of breeders associated these episodes with losses in the litter, which helps to understand that it is not just a “mother’s” problem, but can have an impact on reproductive success.

At home, a simple and very useful measure is to spend a few seconds each day during the first week after giving birth or after a recent heat cycle observing and gently palpating the teats: compare pairs, check for warmth, harder or painful areas, and changes in the skin (redness). This early monitoring is key, as clinical studies indicate that cases detected in the early stages can usually be resolved with medical treatment, while those diagnosed late have a higher risk of abscess formation, mammary necrosis and the need for surgical intervention. In closely monitored breeding populations (e.g., breeding programmes with close veterinary monitoring in two guide dog populations – 3,076 births analysed), clinical mastitis was diagnosed in 13.2% of births, with an average diagnosis around day 16–17 (second–third week) postpartum; and large litters (≥9 puppies) increased the risk (approx. 60% more likely than litters <9); This reinforces the idea that systematic monitoring (and not just “when it is already visible”) changes the prognosis.

The key is to understand the mechanism. The mammary gland produces milk; if that milk is not properly evacuated, it accumulates, increasing intramammary pressure and causing microlesions in the glandular tissue. This phenomenon, called mammary congestion, creates a nutrient-rich local environment that promotes bacterial proliferation. In practical terms: when there are weak puppies that feed poorly, when they always latch onto the same teats, or when there is overproduction of milk, the risk increases. Therefore, it is advisable to check that all puppies are feeding and that they are rotating; if one is systematically left out, you can help by placing it on a less used teat, without forcing it, and making sure that it swallows and breathes well.

Practical fact 🧩

In large litters, rotating puppies between teats is not a “fad”: it is prevention. If they always suckle from the same teats, the others become engorged… and engorgement is the classic precursor to inflammation. 

It is also useful to keep the “nest” clean and dry (change pads frequently), because hygiene in the environment reduces the risk of contamination of nipples and micro-fissures. Microbiological studies of milk in bitches show that it is not always sterile and that, when mastitis or contamination is present, bacteria such as Staphylococcus (skin flora) frequently appear, as well as families compatible with faecal/environmental contamination such as Enterobacteriaceae, in addition to Enterococcaceae. this practical data supports the idea that hygiene of the environment and the nipple, and avoiding micro-lesions due to excessive licking, are not “details” but real prevention.

Mastitis can occur in different contexts: during normal lactation, in situations of milk overproduction, or after pseudopregnancy. The latter is particularly relevant from an epidemiological point of view, as it is estimated that between 50 and 75% of unspayed bitches show some degree of signs of pseudopregnancy throughout their reproductive life. Although not all develop mastitis, milk production without physiological drainage clearly increases the likelihood of mammary inflammation. If pseudopregnancy is suspected (nesting, ‘adopted’ toys, constant licking of the breasts, milk), it may help to avoid stimuli that perpetuate the cycle: remove objects that are ‘mothered’, reduce licking if it causes pain, and increase gentle activity to distract. Important: do not manipulate the gland as if it were an udder; squeezing or massaging it forcefully can worsen the inflammation.

A common mistake is to think that mastitis only occurs after giving birth. In reality, a female can develop mastitis without having had puppies. Pseudopregnancy is a physiological consequence of the luteal phase in dogs, characterised by elevated prolactin levels. Endocrinological studies confirm that this hyperprolactinemia can induce sufficient milk production to cause breast engorgement and pain, even in the total absence of pregnancy. From a practical point of view, this explains why some bitches develop mastitis after each heat. Without preventive measures, these episodes can recur, increasing the risk of chronic breast lesions.

Signs, diagnosis and treatment: when it is urgent and what we do in the clinic

From a clinical point of view, mastitis is an inflammation of one or more mammary glands, usually associated with a bacterial infection. It can range from a mild congestive form to severe cases with abscesses or tissue necrosis. Clinical studies show that approximately 25–30% of diagnosed cases of mastitis already show signs of established bacterial infection at the time of consultation, which explains the importance of seeking veterinary care without delay.

Your vet advises 🐾

During the first 7–10 days postpartum, the most useful “quick check” is this: look + touch gently + smell. If there is marked heat, pain, bad odour or unusual milk (lumpy, with blood or pus), do not wait for it to “mature”: with mastitis, waiting usually makes treatment more expensive. 

The most common signs include enlarged breasts, redness, localised heat, and obvious pain when touched. Many females avoid lying on the affected area or refuse to breastfeed, which can compromise the survival of the litter. In addition, abnormal discharge may appear from the nipples, with thick, lumpy, bloody, or purulent milk. At home, if there is visible discharge, it is prudent not to “squeeze” the nipple; simply clean gently with moistened gauze (warm water or saline solution), dry thoroughly and observe. If there is a strong odour, pus, blood, or the mother is listless, this combination is reason for prompt consultation.

Did you know?

Mastitis can start by affecting only one breast. If the female always lies down on the same side or protects an area when touched, this is sometimes the first clue before fever sets in. 

When abnormal discharge appears—bloody, purulent, or foul-smelling milk—there is usually already an active infection, and studies show that these cases are more likely to be accompanied by fever and general malaise. In addition, it has been noted that contaminated milk may be associated with serious neonatal disease. A classic study in bitches evaluated milk bacteriology and its relationship with symptoms in puppies, emphasising that bacterial contamination of milk can be associated with neonatal pathology, including symptoms compatible with septicaemia in puppies. Therefore, when the mother has obvious signs of mastitis, protecting the litter (and assessing lactation management on a case-by-case basis) is not optional; it is part of the treatment.

In the early stages, the female may not show systemic signs. However, once fever, apathy or anorexia appear, we are talking about an inflammatory process that is no longer localised. Clinical literature indicates that cases with systemic involvement have a clearly higher risk of complications and hospitalisation. A practical method for guardians: if the animal is acting strangely, look for indirect signs (tremors, faster breathing, refusal to eat, isolation); in lactating dogs/cats, a sudden “change in character” is usually a clue to pain or fever, not a whim.

During the consultation, the aim is to assess the severity of the condition and rule out complications. Clinical examination remains the main tool, but in moderate or severe cases, additional tests are used. Bacterial cultures allow antibiotic treatment to be adjusted and have been shown to improve the clinical resolution rate compared to prolonged empirical treatments. Breast ultrasound, meanwhile, is particularly useful for detecting abscesses, whose size and location determine therapeutic management. While waiting for the appointment, the most useful thing the guardian can do is provide specific information: when it started, whether the mother is breastfeeding, whether one breast is “much worse”, whether there is discharge and what it is like (colour/consistency/smell), and whether there are any general signs (lethargy, vomiting, fever).

Treatment is tailored to each situation, but is based on controlling pain, inflammation and infection. Clinical studies agree that early treatment significantly reduces the duration of symptoms and the likelihood of surgery. In uncomplicated mastitis, the outcome is usually favourable within a few days with appropriate medical treatment. At home, two practical measures are often very valuable: keeping the birthing area clean and dry, and ensuring that the mother has constant access to water. Breastfeeding management is decided on a case-by-case basis: in some cases it can be continued with precautions; in others, it is necessary to limit or temporarily suspend it to protect the mother and her young, and the guardian may then need support to feed the puppies safely.

In advanced cases, with abscesses or necrosis, the literature describes surgical intervention rates that can exceed 20–30%, reinforcing the importance of early diagnosis. These cases often require prolonged treatment and can permanently compromise lactation. In this regard, applying heat, performing intense massage or using topical products without professional guidance can worsen the injury and delay healing; if any local measures are taken, they should be as directed by the veterinary surgeon and using a gentle and controlled technique.

Realistic prevention: other postpartum complications and the role of sterilisation

Postpartum carries other significant risks in addition to mastitis. Puerperal hypocalcaemia (eclampsia), for example, is estimated to affect approximately 0.5–1% of lactating bitches, with a higher incidence in small breeds and large litters. It is a life-threatening emergency that requires immediate treatment. Postpartum uterine infections, although less common than pyometra, are also well documented and can coexist with mastitis in septic cases. A very practical point for guardians: if a nursing mother begins to tremble, pant, stiffen, become extremely nervous or walk strangely, it is not “anxiety”: it may be a metabolic emergency. It is also useful to monitor postpartum vaginal discharge: if there is a strong odour, pus, lethargy or fever, this is a reason for urgent consultation. The general rule is simple: if there is a poor general condition, it is not a problem “only of the breasts” or “only of the uterus”; it is the body saying “I need help”.

When you do not wish to breed, sterilisation is one of the most effective preventive measures. By eliminating the hormonal cycles responsible for pseudopregnancy, the risk of recurrent mastitis is significantly reduced. Various population studies confirm that spayed bitches have a virtually zero incidence of mastitis not associated with mammary tumours, making this procedure a key tool in preventive medicine. For the owner, this translates into fewer postpartum emergencies, fewer complex treatments, and more predictable healthcare planning.

Sources and recommended reading (to copy and paste)

Canine and Feline Mastitis: Pathogenesis, Diagnosis and Treatment. Journal of Veterinary Science & Medical Diagnosis. Clinical review of mechanisms, bacteriology and therapeutic management.

https://www.longdom.org/open-access/canine-and-feline-mastitis-pathogenesis-diagnosis-and-treatment-2161-0541-1000182.pdf

Mastitis in the Bitch. In: Canine and Feline Theriogenology, Johnston SD et al. Reference chapter on veterinary reproduction.

https://www.sciencedirect.com/book/9780721693200/canine-and-feline-theriogenology

Pseudopregnancy in Dogs. MSD Veterinary Manual. Clear review of pathophysiology and clinical consequences.

https://www.msdvetmanual.com/reproductive-system/pseudopregnancy/pseudopregnancy-in-dogs

Postpartum Disorders in the Bitch. MSD Veterinary Manual. Postpartum complications and their clinical management.

https://www.msdvetmanual.com/reproductive-system/postpartum-disorders/postpartum-disorders-in-the-bitch