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Mastitis (Mammary Gland Inflammation) in Dogs

Occurrence: common
Location of illness: Abdomen/pelvis

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

Mastitis in dogs is an inflammation of the mammary glands that commonly occurs in lactating bitches. This condition can be caused by bacterial infections, injuries, or other factors that lead to swelling, redness, and pain in the affected glands.

The most important facts at a glance

Mastitis in dogs is an inflammation of the mammary glands, often caused by bacterial infections such as staphylococci or streptococci. These bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. can enter the glands through small injuries to the teats. Other causes include hormonal changes or incomplete emptying of the mammary glands, leading to milk stasis. The symptoms include swollen, painful, and reddened mammary glands, fever, reduced appetite, and apathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest.. A diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made by clinical examination and laboratory analysis of the milk. Treatment includes antibiotics, pain relievers, and anti-inflammatory drugsAnti-inflammatory drugs are medications that reduce inflammation. They can be divided into nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids and are used in dogs and cats to reduce Inflammatory conditions and Pain.. In severe cases, surgery may be required to remove abscesses. Early treatment significantly improves the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop.. Preventative measures include a clean environment, a balanced diet, and regular monitoring of the mammary glands. Research focuses on new diagnostic methods, the study of bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease., genetic factors, and the development of vaccines. The studies aim to improve treatment and reduce the need for antibiotics. In the long term, this could significantly improve the health of dogs through improved preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. and treatment of mastitis.

Causes

The mammary glands of bitches consist of glandular tissue that produces milk proteinProteins are large molecules made up of amino acids and play an essential role in almost all biological processes. They are necessary for building body tissue, the function of the immune system, and as enzymes for metabolic reactions. and fat to nourish puppies. During lactationLactation refers to the production and secretion of milk by the mammary glands of female mammals after giving birth. It serves to nourish the offspring. Lactation problems in dogs and cats can cause health problems for both mother and puppies/kittens., these glands are particularly active and susceptible to infections, as the bitch’s immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. is more stressed during this phase. The mammary glands are usually arranged in several pairs along the bitch’s abdomenThe abdomen, also known as the abdominal cavity, is the part of the body located between the rib cage and the pelvis. It houses several important organs, including the stomach, liver, kidneys, intestines, and spleen..

A common cause of mastitis is a bacterial infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. BacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. such as staphylococci or streptococci can enter the glands through small injuries to the teat or surrounding tissue. These injuries can be caused by the puppies suckling or by external influences such as scratching.

Another cause can be the incomplete emptying of the mammary glands, which leads to a backflow and subsequent inflammation. This can happen if the puppies do not empty all the glands evenly or if the mother bitch does not empty all the glands for other reasons.

Hormonal changes or a weakened immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. can also increase the risk, as they reduce the bitch’s natural defenses against infections.

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

The symptoms of mastitis in dogs are often easy to recognize. Affected bitches often show signs of discomfort and pain, especially when nursing the puppies. The affected mammary glands are swollen, reddened, and feel warm to the touch.

In some cases, the bitch may also develop a fever, which indicates a systemic infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. Decreased food intake and lethargy may also occur. The milk may become discolored, bloody, or purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness., which is a clear sign of an infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..

The puppies may also show signs of discomfort if they consume infected milk, which can lead to diarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems. or other gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. problems.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of mastitis usually begins with a thorough clinical examination by the veterinarian. The entire mammary gland is palpated to identify swellings, temperature changes, or secretions. Close observation of the bitch and her puppies can also provide valuable clues.

To confirm the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., a milk sample can be taken and examined in the laboratory for the presence of bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. and white blood cells. A bacterial culture and an antibiogram help to identify the exact pathogenA pathogen is a microorganism or virus that can cause disease in its host. Pathogens include bacteria, viruses, fungi, and parasites. and determine the most appropriate antibiotic.

In severe or unclear cases, additional diagnostic measures such as blood tests or ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. examinations may be necessary to determine the extent of the inflammatory conditions and possible complications.

Therapy

The treatment of mastitis often requires a combination of drug and supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. measures. Antibiotics are usually prescribed to fight the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. The choice of antibiotic is ideally based on an antibiogram to maximize effectiveness.

Pain relievers and anti-inflammatory drugsAnti-inflammatory drugs are medications that reduce inflammation. They can be divided into nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids and are used in dogs and cats to reduce Inflammatory conditions and Pain. can be administered to relieve the pain and the inflammation. In some cases, it may be necessary to regularly empty the affected glands, either manually or through the puppies, to reduce milk stasis.

Good hygiene is crucial to prevent the spread of infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. This includes regular cleaning of the teats and surrounding area, as well as monitoring the puppies for signs of illness.

In severe cases, where abscess formation or tissue necrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems. has developed, surgical intervention may be required to remove the affected tissue.

Prognosis and follow-up care

The prognosis for mastitis depends on the severity of the disease and the timing of treatment. Early detected and treated cases usually have a good prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop., and the bitches recover completely without permanent damage.

However, untreated or severe cases can cause complications such as abscess formation or systemic infections that require longer and more intensive treatment. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. may be more cautious in such cases.

Long-term consequences for milk production or the well-being of the bitch are rare if the mastitis is treated appropriately. However, careful follow-up and monitoring are important to avoid relapses.

Prevention

The preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of mastitis begins with good care of the lactating bitch. This includes ensuring that the environment is clean and low-stress to avoid injuries and infections. A balanced diet and adequate hydration support the bitch’s immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body..

Regular checks of the mammary glands for signs of swelling or irregularities can help to identify problems early. The even emptying of all mammary glands by the puppies or through manual measures can also help to avoid milk stasis and inflammatory conditions.

In some cases, especially if a bitch has already had an episode of mastitis, the veterinarian may recommend preventive measures or special treatments to minimize the risk of a relapse.

Outlook on current research

Research on mastitis in dogs is currently focused on several key areas. An important area is the development of new diagnostic methods to detect the disease early and accurately. Scientists are working on tests that can identify specific biomarkers in the blood or milk to make the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. faster and less invasiveInvasive describes medical procedures or pathogens that enter the body or penetrate tissue. In medicine, invasive procedures can range from minimally invasive techniques to open surgery.. Such tests could also help to distinguish between bacterial and non-bacterial mastitis, which is crucial for the choice of treatment.

Another area of research is the investigation of the bacterial pathogens that cause mastitis. By understanding the bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. that are most commonly involved, targeted antibiotics can be developed. In addition, research is being conducted on the emergence of antibiotic resistanceResistance refers to the ability of microorganisms to withstand the effects of antibiotics, antifungals, or other antimicrobial drugs. Resistance can also refer to the body's ability to be insensitive to diseases or toxins., as this is a growing problem in veterinary medicine. Researchers are investigating alternative treatment methods, such as the use of probiotics or herbal remedies, to reduce the need for antibiotics.

Researchers are also interested in the genetic and environmental factors that influence susceptibility to mastitis. By identifying genetic markers associated with increased susceptibility, breeders may be able to minimize these traits in the populationIn veterinary medicine, the term population refers to a group of animals of a particular species living in a specific geographic area or environment.. Environmental studies focus on factors such as nutrition, hygiene, and stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. management that can increase the risk of mastitis.

In addition, there are efforts to develop vaccines against the most common mastitis pathogens. Research in this area is still in its early stages, but shows promising approaches. An effective vaccineA vaccine is a substance that stimulates the immune system to develop immunity against specific pathogens without causing the disease itself. Vaccines may contain weakened or inactivated pathogens, toxoids, or recombinant antigens. could significantly reduce the occurrence of mastitis and reduce the dependence on antibiotics.

Another fascinating area of research is the role of the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. in defending against mastitis. Scientists are investigating how the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. of dogs responds to an infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. and why it fails in some cases to fight the disease. These findings could lead to the development of immunotherapies that strengthen the body’s natural defense system.

Research on mastitis in dogs is promoted through international collaborations and the exchange of data and knowledge. This makes it possible to quickly translate the latest scientific advances into practice and improve the health of dogs worldwide. While many of these research projects are still ongoing, they offer hope for new and improved ways to prevent and treat mastitis in dogs.

Frequently asked questions (FAQs)

What is Mastitis in Dogs? Mastitis is an inflammation of the mammary glands in female dogs, often caused by a bacterial infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. It usually occurs during lactationLactation refers to the production and secretion of milk by the mammary glands of female mammals after giving birth. It serves to nourish the offspring. Lactation problems in dogs and cats can cause health problems for both mother and puppies/kittens. but can also occur outside of this phase.
What symptoms does a dog with mastitis show? Symptoms include swollen, painful mammary glands, fever, lethargy, loss of appetite, and sometimes purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. or bloody milk discharge. In severe cases, abscess formation can occur.
How is mastitis diagnosed in dogs? The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually made by physical examination and anamnesis. To confirm, blood tests, milk analysis, and microbiological cultures can be used to identify the pathogenA pathogen is a microorganism or virus that can cause disease in its host. Pathogens include bacteria, viruses, fungi, and parasites..
What treatment options are available for mastitis? Treatment usually includes the administration of antibiotics, pain relievers, and anti-inflammatory drugsAnti-inflammatory drugs are medications that reduce inflammation. They can be divided into nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids and are used in dogs and cats to reduce Inflammatory conditions and Pain.. In severe cases, surgical drainageDrainage refers to the removal of fluid from body cavities, Wounds, or inflamed areas, often using a tube or other device. It is used to prevent infection and promote healing. or removal of the affected tissue may be necessary.
Can mastitis be prevented in dogs? Good hygiene and regular monitoring of the mammary glands during lactationLactation refers to the production and secretion of milk by the mammary glands of female mammals after giving birth. It serves to nourish the offspring. Lactation problems in dogs and cats can cause health problems for both mother and puppies/kittens. can help prevent mastitis. A balanced diet and stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. management also contribute to preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring..
Is mastitis contagiousContagious means infectious. Diseases that can easily be transmitted from one animal to another or from animals to humans are referred to as contagious. in dogs? Mastitis itself is not contagiousContagious means infectious. Diseases that can easily be transmitted from one animal to another or from animals to humans are referred to as contagious., but the bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. that cause it can spread through direct contact or contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. surfaces. Hygiene is therefore important to prevent spread.
Can male dogs get mastitis? While male dogs cannot get mastitis in the traditional sense because they do not have functioning mammary glands, they can suffer from other forms of mammary gland disease.
How long does it take for mastitis to heal in dogs? The healing time depends on the severity of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. and the chosen treatment. With early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment, improvement can occur within a few days, while severe cases can take weeks.
Can a dog breastfeed normally again after mastitis? In most cases, a dog can breastfeed normally again after successful treatment of mastitis. However, it is important to keep the puppies away from the affected teat during treatment.
Are certain dog breeds more susceptible to mastitis? There is no clear evidence that certain breeds are more susceptible. Susceptibility depends more on individual factors such as geneticsGenetics is the science of genes, heredity, and the variation of organisms. It studies how genetic information is passed from generation to generation and how it influences the development, appearance, and behavior of living things., hygiene practices, and general health.