Why Are My Female Dogs Nipples Sticking Out?

Female dogs’ nipples may become enlarged and prominent for a variety of reasons. This article will cover the main causes of protruding nipples in female dogs, including heat cycles, pseudopregnancy, actual pregnancy, nursing, and certain diseases. We’ll also discuss when you should see the vet about your dog’s enlarged nipples, how underlying conditions are diagnosed and treated, and tips for caring for your dog.

When Female Dogs’ Nipples Become Prominent

Female dogs’ nipples becoming prominent is a normal part of their development and reproductive cycle. The mammary glands begin to develop at around 3 weeks of age, but they usually remain small and inconspicuous until puberty. As female dogs go into their first heat cycle at around 6 months of age, increased estrogen levels cause the mammary glands to enlarge and the nipples to become prominent and erect (1). This is in preparation for potential pregnancy and nursing puppies after breeding. The swelling and darkening of the nipples at this time is normal and expected in intact (unspayed) female dogs as they reach sexual maturity.

The heat cycle itself lasts around 3 weeks or 21 days on average (2). During this time, the dog will go through different phases, with the nipples remaining enlarged throughout. The nipples may increase a bit more in size if the dog gets pregnant from breeding during her heat. They will return to a normal, flatter appearance after the heat cycle finishes, unless the dog becomes pseudopregnant or pregnant. So prominent nipples in a 6+ month old intact female dog indicate she is in heat and going through her normal reproductive cycle.

Signs of Heat Cycle

A female dog’s heat cycle causes physical and behavioral changes. One of the earliest signs is swelling and enlargement of the vulva, according to veterinarians from VCA Animal Hospitals (https://vcahospitals.com/know-your-pet/estrus-cycles-in-dogs). Discharge from the vagina will usually follow within a few days. The discharge is often bloody at first and then becomes lighter in color and watery. WebMD reports that the discharge can last for around 9 days (https://www.webmd.com/pets/dogs/how-tell-if-dogs-heat).

Behavioral changes are also common when a female dog is in heat. The Spruce Pets lists some typical behaviors like nervousness, restlessness, and agitation (https://www.thesprucepets.com/signs-your-dog-is-in-heat-3385379). Female dogs will become very receptive to mating during this time and may try to escape or run away to find male dogs. They tend to pay less attention to commands and can become territorial over toys or food. Excessive licking of the genital area is also frequently observed.

Owners should keep a close eye on their female dog when she is in heat to avoid unwanted matings. It’s best to avoid dog parks and limit interactions with unknown dogs during this time. Providing toys, chews, or puzzles can help ease restlessness and agitation. The heat cycle lasts around 2-4 weeks on average.


Pseudopregnancy, also known as false pregnancy, is a common condition that occurs in unspayed female dogs. It happens when progesterone levels drop after a heat cycle, triggering hormonal and physical changes similar to those seen during pregnancy. According to vcaanimalhospitals.com, nearly 50-75% of unspayed female dogs experience pseudopregnancy after estrus.

The most noticeable sign of pseudopregnancy is enlarged mammary glands and nipples. The drop in progesterone stimulates prolactin production, which causes the mammary glands to swell in preparation for nursing puppies. Even though the dog is not actually pregnant, her body thinks it is. The nipples become enlarged, red, and veiny during this time.

Other pseudopregnancy symptoms include nesting behavior, mothering inanimate objects, lethargy, vomiting, and abdominal distension. Most dogs will return to normal on their own after 2-3 weeks. However, the enlarged nipples may persist for up to 1-2 months. If the symptoms last longer than a month, veterinary attention is recommended.


A dog’s nipples will often become more prominent and enlarged during pregnancy as the body prepares for nursing puppies. According to Dog Spoiling Made Easy, one of the early signs of pregnancy in dogs is enlarged nipples, which occurs around 14-15 days after conception. As the pregnancy progresses, the dog’s mammary glands will begin producing milk, which causes the nipples to swell in preparation for breastfeeding once the puppies are born.

The hormones prolactin and oxytocin play an important role in nipple enlargement during canine pregnancy. Prolactin levels increase throughout pregnancy which triggers milk production. Oxytocin causes the milk to be released from the mammary glands when the puppies suckle. The combination of milk production and release is what causes the nipples to become more pronounced.

It’s important to provide ample nutrition and care for a pregnant dog to support the mammary changes happening. Make sure she receives high-quality puppy food and regular veterinary checkups. Gentle massage of the mammary glands can also help prepare them for nursing. Enlarged nipples are a normal part of pregnancy, but call your vet if you notice any abnormal discharge or inflammation which could indicate an infection.

Nursing Female Dogs

It’s normal for a female dog’s nipples to become enlarged and prominent during nursing. When a female dog is lactating and producing milk for her puppies, her mammary glands will swell and cause the nipples to protrude visibly. The hormones prolactin and oxytocin are responsible for milk production and this physiological state of lactation keeps the mammary glands enlarged until the puppies are weaned.

According to veterinarians, the size and appearance of nursing dogs’ nipples can vary based on factors like litter size, stage of nursing, and overall health. The more puppies a mother dog is nursing, the more inflated and pronounced her nipples generally become. Toward the end of nursing, as milk production starts slowing down, the enlarged nipples may begin shrinking back to normal.

While temporarily enlarged nipples are normal for a nursing dog, the mammary glands should not be painfully hard, hot, or inflamed. Signs of mastitis such as redness, swelling, pain, and pus warrant a vet visit for treatment (https://vcahospitals.com/know-your-pet/mastitis-in-dogs). With proper care and weaning of the puppies, the mammary glands and nipples should return to regular size after nursing ends.

Diseases Causing Enlarged Nipples

Certain diseases and conditions can cause a female dog’s nipples to become enlarged and prominent abnormally. Two of the most common causes of pathological nipple enlargement in dogs are mastitis and mammary tumors.

Mastitis is a bacterial infection of the mammary glands that causes inflammation, swelling, and reddening of the breast tissue. The nipples often become enlarged, warm, and painful to the touch. Mastitis most commonly affects female dogs that are nursing puppies, but it can occur in non-lactating dogs as well. Treatment involves antibiotics and anti-inflammatories. In severe cases, surgery may be required to remove infected mammary glands.https://dogscable.com/why-are-my-dogs-nipples-enlarged-after-heat/

Mammary tumors are abnormal growths that develop in the breast tissue. They often cause swelling and enlargement of the nipples. Mammary tumors are the most common type of tumor in unspayed female dogs. They can be benign or malignant. Treatment depends on the type, size, and location of the tumor, and may involve surgical removal, chemotherapy, or radiation. Early detection and treatment is key for the best prognosis.

When to See the Vet

Enlarged or swollen nipples in female dogs are often normal when associated with the heat cycle, pregnancy, pseudopregnancy, or nursing. However, if a spayed female or a female that is not in heat, pregnant, or nursing has enlarged nipples, it is best to have her evaluated by a veterinarian.

Some conditions that may cause abnormal nipple enlargement outside of reproduction and nursing include:

  • Mastitis (breast infection)
  • Mammary gland tumors
  • Hormonal disorders
  • Trauma to the nipples

A veterinarian can perform tests to determine if there is an underlying medical issue causing the swollen nipples and provide appropriate treatment. It is especially important to have enlarged nipples assessed in spayed females or those not reproductively active, as this is considered abnormal. Prompt veterinary care can identify and address conditions early before they potentially worsen.



Treating Underlying Conditions

If the enlarged nipples are caused by an underlying condition like mastitis or mammary tumors, treatment will focus on resolving the underlying issue. Mastitis is an infection of the mammary glands that causes swelling, pain, and redness. It can often be treated with oral antibiotics like amoxicillin or cephalexin, as well as anti-inflammatory medication for pain relief (1). Warm compresses can also help soothe mastitis. In more severe cases, the infected mammary gland may need to be surgically removed (2).

Mammary tumors are abnormal growths of the breast tissue. Depending on the type and stage of tumor, treatment options include surgical removal, chemotherapy, or radiation. Early identification and treatment of mammary tumors is key to positive outcomes (3). In addition to treating the tumor itself, any discharge, swelling, or inflammation of the nipples should be managed with medication and warm compresses to keep the area clean.

By treating underlying mastitis, mammary tumors, or other conditions causing enlarged nipples in female dogs, the enlargement and discomfort can be reduced and potentially eliminated.


(1) https://vcahospitals.com/know-your-pet/mastitis-in-dogs

(2) https://www.webmd.com/pets/dogs/what-to-know-about-mastitis-in-dogs

(3) https://www.merckvetmanual.com/reproductive-system/reproductive-diseases-of-the-female-small-animal/mastitis-in-small-animals


In summary, female dogs’ nipples becoming enlarged or protruding is often a normal occurrence. The most common reasons for swollen nipples in female dogs are heat cycles, pseudopregnancy, and pregnancy/nursing. However, there are also some concerning diseases like mastitis or tumors that could cause nipple changes as well.

Enlarged nipples alone are usually not an emergency unless they appear infected, inflamed, or your dog seems in pain. But it’s a good idea to have your veterinarian take a look if the nipple changes seem abnormal or persist longer than expected. Getting exams and tests done can help identify or rule out any underlying medical issues.

With proper treatment for any conditions causing nipple enlargement, along with spaying dogs not intended for breeding, owners can help keep their female dogs’ nipples healthy and prevent recurring changes. If the nipples appear normal otherwise, try not to worry too much about prominence alone. But when in doubt, don’t hesitate to contact your veterinarian.

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