My Male Dog Has a Swollen Nipple

By Matthew Nesbitt, Journalist specialized in animal research. April 6, 2020
My Male Dog Has a Swollen Nipple

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Although they often go unnoticed due to their small size, male dogs also have nipples. While a female dog has different uses for their breasts once they give birth to young, males also have mammary gland tissue which can be very sensitive. Even though they cannot lactate, male dogs can suffer injury or disease to their mammary glands. Often, the swelling of the dog's nipple will first alert us to a problem.

This AnimalWised article discusses what might have happened if your male dog has a swollen nipple. Of course, we need to pay close attention to any change in our dog's skin, even if the problem appears to be subcutaneous (i.e. under the skin).

You may also be interested in: My Dog has a Swollen Throat

Breast cancer in male dogs

It is understandable we might associate breast cancer in dogs with females as mammary gland tumors are relatively rare in male dogs[1]. Females which have not been sterilized are particularly prone to this disorder. However, it is possible for a male dog with a swollen nipple to have a tumor related problem.

In male dogs, the relatively few cases of mammary gland tumors which have been recorded generally affect senior dogs over the age of 10 years. In the vast majority of these cases the tumors will be benign.

Tumors in a dog's nipple or breast will present as lumps which are usually subcutaneous, i.e. under the skin. However, it is possible for the skin to ulcerate, so you may see broken skin on the nipple. We should not wait for them to grow further, but take them to the veterinarian as soon as possible.

Especially with bitches, the most common form of treatment is surgical removal of the tumor. Before this occurs, a biopsy of the inflammation is usually taken. It can then be analyzed to see what type of tumor it is and inform the course of treatment. It is important to remember that benign mixed tumors affect the mammary glands and soft tissues more than other areas[2]. This means if your dog's nipple is swollen, while possible, it is statistically unlikely to be life-threatening.

My male dog has a swollen nipple due to infection

The inflammation of breast tissue is known as mastitis. This often affects female dogs during lactation due to the abrasiveness of the puppies' suckling. Two types of mastitis have been observed, galactostasis and acute septic mastitis. Both cases require the intervention of the veterinarian.

In the case of galactostasis, there is an accumulation of milk that swells the breasts, causing pain and heat. It can occur both during lactation and phantom pregnancies. For this reason, galactostasis is not possible to happen in male dogs.

In acute septic mastitis, there is an infection or abscess in one or more mammary glands. The inflammation is caused by bacteria that enter the inside of the breast through a wound or other opening present on the skin. The result is an infection which abscesses and causes the wound to worsen. In cases of infection and in addition to having a swollen nipple, the dog may display symptoms of:

Although mastitis can occur in a male dog, if they have an swollen nipple, it is rarely for this reason. However, there could be an abscess present for another reason. An abscess causes a build-up of pus under the skin due to infection. The resulting lump or swollen nipple could be the consequence of:

  • A bite
  • A scratch (often from another animal)
  • A foreign body that has become stuck under the skin
  • Cut from brush
  • Insect sting

Abscesses must be seen by a veterinarian. If the build up of pus is extensive, they may need draining. In the case of foreign bodies which have entered the skin, they will need to be removed. A course of antibiotics may need to be prescribed if the infection is advanced.

As you can see there are various reasons why a male dog will have a swollen nipple, but an infection leading to abscess if one of the most common. These can vary in severity, but are usually very treatable and don't necessarily indicate a serious problem. We also need to be careful and ensure the swelling is in the breast or nipple tissue. In some cases, the swelling could be in the abdomen and indicate a serious issue such as bloat.

If you see seepage from the dog's nipple, you can look at our article on why your dog's nipple is leaking for more information.

My Male Dog Has a Swollen Nipple - My male dog has a swollen nipple due to infection

My male dog has a black nipple

While a male dog having a swollen nipple is not necessarily a causes for concern, if they are turning black it may be due to hyperestrogenism. As the name suggests, this is due to excess levels of estrogen. This can occur when there is an overproduction of these hormones in the dog's testicles. This issue is associated with testicular tumors and occurs most frequently in specimens which are over the age of six years.

These types of tumor which cause hyperestrogenism are rare in non-retained testicles. In these cases they can be seen as enlargement or the presence of enlarged or hardened masses. Retained testicles in a dog is known as cryptorchidism and occurs when one of more testes do not descend into the scrotum. The majority of cases of hyperestrogenism occur in dogs with retained testicles and it is possible to observe a lump or swelling in the inguinal area.

Symptoms which indicate hyperestrogenism include enlarged mammary glands and nipples, as well as discoloration. If your male dog has a swollen nipple, it is possibly due to this problem. You may also notice the foreskin becomes enlarged and there are symmetrical changes in the skin and hair, especially in the genital region. There is often dryness in the skin and accompanying alopecia where the dog's hair falls out. The darkening of the skin may extend to the nipple, causing it to turn black. Treatment is usually castration.

My Male Dog Has a Swollen Nipple - My male dog has a black nipple

Other cause of swollen nipples in male dogs

While the above reasons are more specific for a male dog to have a swollen nipple, there are other common skin issues which may affect it. They include:

  • Parasites: when an external parasite burrows into the skin of the nipple, it can cause a lump or swelling. Proper deworming treatment and checking their skin regularly can help prevent this.
  • Allergies: if the dog is allergic to something, the nipple may swell if it has come in touch with it.

These issues can affect male or female dogs equally. If you are in any doubt, contact your veterinarian to achieve a suitable diagnosis of the problem for your dog.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to My Male Dog Has a Swollen Nipple, we recommend you visit our Other health problems category.


1. Saba, C. F., et al. (2007). Mammary Gland Tumors in Male Dogs. Journal of Veterinary Internal Medicine, 21(5), 1056-1059.

2. Choi, J-W., Yoon, H-Y., & Jeong, S-W. (2016). Clinical Outcomes of Surgically Managed Spontaneous Tumors in 114 Client-owned Dogs. Immune Network, 16(2), 116-125.

  • Arias J. I., Paredes, E., & Torres, C. G. (2015). Mammary carcinoma in a male canine: Clinical and immunohistochemical characterization. Arch. Med. vet., 47(1).
  • Bearss J. J., Schulman, F. Y., & Carter, D. (2011). Histologic, Immunohistochemical and Clinical Features of 27 Mammary Tumors in 18 Male Dogs. Vet. Pathol. Mar., 24.
  • Carlson, D. G., & Giffin, J. M. (2002). Practical Canine Veterinary Manual. Madrid: El Drac.

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