Can Dogs Nipples Leak Milk If Not Pregnant?

Milk or fluid leaking from a dog’s nipples is not normal, especially if the dog is not pregnant or nursing puppies. This condition can occur in both male and female dogs and can be caused by several reasons. Understanding the causes and seeking prompt veterinary care is important to relieve discomfort, treat any underlying condition, and prevent complications.

This article provides an overview of dog nipple anatomy, explains common reasons for nipple discharge in dogs, and discusses diagnosis and treatment options. Knowing the facts can help dog owners identify abnormal nipple secretions early and take appropriate action.

Anatomy of Dog Nipples

Dogs, both male and female, typically have between 8 to 10 pairs of nipples. These nipples are located on two parallel rows that run along the dog’s abdomen from their chest to their groin area.1 The nipples are connected to mammary glands buried beneath the skin’s surface that produce milk when dogs are nursing puppies.

The mammary glands release oxytocin when dogs nurse their puppies, which stimulates milk production and causes the milk to be ‘let down’ so it can be consumed. The nipples expand and protract slightly to allow puppies to nurse. While male dogs have nipples, they do not have functioning mammary glands that produce milk. Only female dogs produce milk to nurse their young.

False Pregnancy

Pseudopregnancy, also known as false pregnancy, is a common condition that occurs in intact female dogs who are not actually pregnant. It happens when the female dog shows various symptoms of pregnancy even though she has not been bred. According to one report, up to 87 percent of intact female dogs may show signs of false pregnancy at some point in their lives [1].

False pregnancy occurs after the female dog goes through an estrus or heat cycle. During this time, her progesterone levels rise sharply which causes physical and behavioral changes that mimic pregnancy. As progesterone levels decline, the bitch’s body thinks she is undergoing a normal dog pregnancy. This triggers the release of prolactin which leads to milk production and motherly behaviors [2].

Some of the most common signs of false pregnancy in dogs include milk leakage or swelling of the mammary glands, nesting behaviors, mothering inanimate objects, lethargy, vomiting, and abdominal enlargement that mimics a growing fetus. These symptoms typically last for 2-3 weeks after the heat cycle ends though they can persist up to 12 weeks in some cases [3].

While pseudopregnancy itself is not dangerous, it can lead to mastitis or mammary gland infections if the breasts become engorged. It’s important to consult your veterinarian if your intact female dog shows any of these concerning signs after a heat cycle concludes.


Mammary Gland Tumors

Mammary gland tumors are the most common type of tumors in dogs, accounting for around 42% of all tumors diagnosed in female dogs (Veterinary Society of Surgical Oncology). The lifetime risk for mammary tumors in female dogs is 23-34% (Moe 2001).

The incidence rates vary by breed, with the highest rates seen in Boxers, English Setters, English Springer Spaniels, and Dachshunds (Moe 2001). Recent studies have found annual incidence rates ranging from 22.72% to 61.45% depending on the breed (Zheng et al. 2022).

Symptoms of mammary tumors include lumps or swelling in the breasts, abnormal nipple discharge, ulceration, reddening of skin, and enlarged lymph nodes. Tumors can range from benign to malignant, with malignant tumors tending to be fast growing. Early detection and treatment is key for the best prognosis.


Mastitis is the inflammation of the mammary glands and ducts. It is most commonly caused by bacterial infection, often streptococcus or staphylococcus species. Mastitis can occur in both pregnant and non-pregnant female dogs, as well as dogs who are lactating or have pseudo-pregnancies. Certain breeds like Boxers, Dobermans, and English Springer Spaniels are at higher risk.

Symptoms of mastitis include swelling, redness, heat, and pain in the affected mammary gland. The dog may act lethargic, lack appetite, and run a fever. There may be abnormal discharge from the nipple that is yellow, green, or bloody. Mastitis usually only affects one gland, but sometimes multiple glands are involved.

Veterinary treatment is needed for mastitis. Antibiotics, anti-inflammatories, and fluid therapy are typically given. In severe cases, the affected mammary gland(s) may need to be surgically removed. At home care includes hot compresses, veterinarian-prescribed medication, and keeping the area clean.

Preventing mastitis involves maintaining hygiene of the mammary glands during lactation. Early weaning of puppies may also reduce risk. Checking mammary glands regularly for signs of infection allows early veterinary treatment if needed.

Other Causes of Nipple Discharge

In addition to the more common causes of nipple discharge like false pregnancy and mastitis, there are some less common reasons that may lead to nipple leakage in dogs:

Medication side effects – Some medications like steroid therapy or anti-seizure drugs can cause increased prolactin levels and milk secretion. According to, “Drugs like phenothiazine, sulpiride, haloperidol, metoclopramide, and domperidone all may contribute to lactation in dogs.”

Hyperadrenocorticism (Cushing’s disease) – Dogs with Cushing’s disease tend to have increased cortisol levels which can sometimes stimulate milk production and lead to nipple discharge. As noted in an article by VCA Hospitals, “The high cortisol levels seen with this disease can cause lactation and swollen mammary glands.”

Mammary gland cysts – Fluid-filled cysts in the mammary glands may rupture and lead to nipple leakage. These cysts are generally benign but can become infected or problematic if they rupture.

Spaying complications – In rare cases, dogs spayed while lactating or in estrus may continue to have mammary gland secretions after surgery. This discharge usually resolves on its own.

When to See the Vet

It’s recommended to have a vet examine your dog if they have persistent nipple discharge that does not resolve on its own within a few days. The vet will perform a physical exam of the dog’s mammary glands and may run tests to determine the underlying cause.

Some of the tests the vet may perform include:

  • Cytology – Microscopic examination of cells from discharge fluid
  • Biopsy – Removing a small sample of tissue for examination
  • Blood tests
  • Diagnostic imaging – X-rays or ultrasound of mammary glands

These tests can help determine if the cause is an infection, hormone imbalance, or something more serious like a tumor. It’s important to have persistent nipple discharge evaluated, as some causes like cancer require prompt treatment.

Seeing the vet is highly recommended for any abnormalities of the mammary glands and nipple discharge, especially in intact females over 4 years old where mammary tumors are more common. Don’t wait to see if discharge resolves on its own – an exam and testing can identify the cause and confirm if treatment is needed.


The treatment for nipple discharge in dogs depends on the underlying cause. Some common treatment options include:

Mastitis in Dogs – VCA Animal Hospitals

If mastitis is the cause, antibiotics and anti-inflammatory medications are usually prescribed. The antibiotics treat the bacterial infection while anti-inflammatories help manage pain and swelling. In mild cases of mastitis, antibiotics may be enough to resolve the infection and discharge.

Causes of Nipple Discharge in Dogs

For false pregnancy, medication can help suppress lactation and associated discharge. The discharge usually resolves on its own as the false pregnancy runs its course.

If the cause is a mammary gland tumor, surgical removal of the tumor is generally recommended. Chemotherapy or anti-hormone medications may also be options depending on the type of tumor.

The key is to identify and treat the underlying cause. Symptomatic treatment with cold compresses, mild pain medication, and keeping the area clean may provide some relief in the meantime.

Prevention of Nipple Discharge and Mastitis

There are several ways to help monitor your dog’s nipples and reduce the risk of mastitis:

  • Check the nipples daily for any signs of swelling, irritation, or discharge. Look for changes in size, color, or texture.
  • Gently squeeze each nipple to check for any secretion. Note any abnormalities.
  • Keep the nipple area clean and dry. Gently wipe with a warm, damp cloth if needed.
  • Use an Elizabethan collar to prevent licking or chewing of nipples if necessary.
  • Make sure puppies are latching on and nursing normally if the dog is lactating.
  • Wean puppies gradually and allow the mother dog’s milk supply to decrease slowly.
  • Feed a high quality diet and maintain the dog’s ideal body condition.
  • Have any lumps or masses on the breasts evaluated by a vet promptly.
  • Follow post-operative care instructions if the dog has had a mastectomy.
  • Keep the dog’s bedding clean and dry. Change frequently.

Monitoring the nipples and breasts carefully along with proper nursing techniques can help prevent nipple discharge and reduce mastitis risks.


In summary, there are several potential causes for nipple discharge in dogs who are not pregnant. These include false pregnancy, mammary gland tumors, mastitis, and other medical conditions. While some causes may resolve on their own, it’s important to have your dog examined by a vet to get an accurate diagnosis and appropriate treatment.

Key takeaways are that any nipple discharge warrants an evaluation to rule out concerning causes like cancer. Treatment depends on the underlying cause but may include antibiotics, anti-inflammatories, or surgery. Preventative care like spaying can reduce the risk of false pregnancy and mammary tumors.

If you notice any nipple discharge in your dog, don’t hesitate to make an appointment with your veterinarian right away. They can help determine the cause and recommend the best course of action for your dog’s health and comfort.

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