Causes of Nipple Discharge in Dogs

Updated on March 16, 2018
alexadry profile image

Adrienne is a certified dog trainer and behavior consultant, former veterinarian assistant, and author of "Brain Training for Dogs."

What causes nipple discharge in dogs?
What causes nipple discharge in dogs?

How Do Mammary Glands Develop?

Mammary glands are modified sweat glands that are present in both male and female embryos during fetal development. The nipples remain indistinguishable at birth until sex hormones kick into high gear. The female hormones contribute to the development of mammary glands and their secretory function.

Discussion Topics

  1. Understanding Nipples in Dogs
  2. Did Your Know?
  3. Why Does My Dog Have Nipple Discharge?
  4. For Further Reading

Understanding Nipples in Dogs

If you noticed nipple discharge in your dog, you might be concerned because you may have heard that this can be cancer. While cancer is always a possibility, there are several other causes for nipple discharge in dogs. You will therefore need to see your vet for proper diagnosis and treatment. This article is only meant to give an idea of what can cause nipple discharge in dogs as only your vet can determine exactly what your dog has.

First of all, a lesson in dog anatomy. Consider that all dogs have nipples. Male dogs, female dogs, spayed dogs, neutered dogs and, of course, intact dogs. In female dogs, the nipples have an important function; that is, to deliver milk that is produced in the mammary glands so to nourish a batch of hungry puppies.

The mammary glands in dogs are arranged in two rows starting from the chest area all the way up to the groin. Interestingly, according to University of Illinois, the number of glands varies based on the dog's size. While in general dogs may have anywhere between 8 to 12, with 4 to 6 on each side, large breeds are known for having about ten, while smaller breeds are known for having about eight.There are no rules written in stone though as you may sometimes encounter dogs with some extras nipples or some dogs with some missing. If you want to learn more about where they're located, consider that generally large breeds have the following:

  • 1 pair of cranial thoracic teats
  • 1 pair of caudal thoracic teats
  • 1 pair of cranial abdominal teats
  • 1 pair of caudal abdominal teats
  • 1 pair of inguinal teats

Each nipple is surrounded by several openings that are meant to allow milk to excrete when the puppy suckles. You would assume that since male dogs don't have to whelp, Mother Nature would have deprived them of nipples. Instead, just like human men, male dogs have nipples, but they are typically in a rudimentary state. So since the primary purpose of nipples is to excrete milk, it's quite normal to be alarmed when you notice a discharge that takes place when dogs aren't lactating.

A case of mastitis in sheep.
A case of mastitis in sheep. | Source

Why Does My Dog Have Nipple Discharge?

Nipple discharge is more commonly seen in intact female dogs, but spayed female dogs and male dogs may also develop conditions that may cause discharge.

End of Pregnancy

When dogs are nearing the end of pregnancy, their nipples may develop a discharge. The discharge is typically clear or milky in color. The onset time of milk production in dogs varies from one another. Some start developing milk even a week prior, others a day or two prior to give birth and others right after giving birth. When a dog gives birth, oxytocin, the primary hormone associated with labor and delivery, is what triggers lactation and the "let-down" of milk, explains Gen B., a retired veterinarian.


Remember the openings we talked about where milk is secreted for the pups when they suckle? While these openings have an important purpose, one must consider that these same openings may also allow bacteria to enter. It's a good idea to keep an eye on mother dog's nipples. It's not uncommon for mother dog to develop mastitis, the medical term for an infection of the dog's milk producing glands. It's often caused by the puppy's nails scratching the nipples or unsanitary conditions. Symptoms include hot, painful mammary glands, and a pus/bloody discharge from nipples. Mother dog may also become reluctant to nurse. If you suspect your nursing dog has mastitis, see your vet and make sure the puppies don't nurse from the affected nipple as in severe infections the milk can cause serious illness and even death of the puppies. Left untreated, mother dog may develop a fever, loss of appetite and lethargy.

False Pregnancy

A phenomenon owners of intact female dogs must keep in consideration is what is known as "false pregnancy." After a female, intact dog goes in heat, she may develop maternal behaviors such as nesting along with physical signs that are strikingly similar to a real pregnancy. The physical signs include enlarged mammary gland along with nipple discharge, and in some cases, even abdominal distension .This occurs because after a dog's heat, the dog's body will produce high level of progesterone regardless if she is pregnant or not. Generally, signs of false pregnancy develop about a month or two after the dog's heat. Typically, in a dog undergoing false pregnancy, the discharge is seen from multiple nipples at the same; which is quite different from mammary cancer which mostly affects only one, explains veterinarian Dr. K. See your vet to rule out a possible pregnancy or a possible pyometra (infection of the uterus).

An Abscess

In this case, we are talking about an abscess that could have developed as a result of an injury or intrusion of a foreign body. For instance, an abscess may form as a result of a foreign body such as a thorn or small stick that may have introduced bacteria into the skin by the dog's nipple/mammary gland. Then, the puncture closes over, trapping the bacteria inside. This causes local swelling, warmth and sometimes discharge.

Mammary Gland Cancer

Intact, non-spayed dogs are more commonly affected than spayed dogs as they undergo hormonal changes that raise and fall. In dogs who were spayed before the first heat cycle, the chances for developing breast cancer are significantly low, just about 0.5%. Chances are also extremely rare in male dogs. However, the statistics grow higher in female dogs spayed after 2 years of age. When it comes to statistics, 50 percent of dog breast cancer cases are benign, while the remaining 50 percent are not. Non-benign breast cancer in dogs is cancer that has spread to other locations such as the lymph nodes, lungs (causing coughing, labored breathing) or other body parts. Generally, the larger the growth, the bigger the chances that cancer has spread, explains Dr. Daniel A. Degner,a board-certified veterinary surgeon. Symptoms of breast cancer in dogs include a straw-colored, pus-like or bloody discharge from the nipple and presence of small or large nodules within the dog's breast. Mammary tumors are most often seen in the inguinal glands close to the legs. Breast cancer is diagnosed by fine needle aspiration. Here are some typical findings:

  • Fibroadenoma: A benign glandular tumor
  • Mixed Mammary Tumor: as the name implies, these can be either benign or malignant.
  • Adenocarcinoma: malignant
  • Inflammatory Carcinoma: highly malignant ulcerated tumor that spreads quickly and produces pus and discomfort, but luckily, not very common.

As seen, discharge from the nipples in dogs can be caused by various conditions. Some conditions may be easily treated, others are more serious. See your vet if your dog has fluid coming from her nipples.


This article is not to be used as a substitute for professional veterinary advice. If your dog has nipple discharge, see your vet for a proper diagnosis and treatment.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

  • Why does my female Bullpit treat her toy duck like a newborn puppy?

    Is your dog intact? Has she been spayed? If not, then this might be a sign of a false pregnancy.

© 2015 Adrienne Janet Farricelli


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    • profile image


      7 weeks ago

      My female boxer has had 3 litters was keeping her inside but there is a chance she is pregnant cuase she got out one night for abt an hr she is very fat full of milk and she has a dark brown puss coming from one of her nipples only out of one hole the other two holes it looks like collostriaum

    • profile image


      5 months ago

      Why is my female pitull producing blood instead of milk??

    • profile image

      Grayson Morris 

      9 months ago

      Why is my dog have milk coming out of her breast and she's not pregnant swollen breasts

    • profile image

      Priya verma 

      9 months ago

      My 4year lhassa apso have nipple discharge she faced dis problem after 20 days Dr advice surgery to remove uterus she in very pain and don't eat anything from last two days I can't afford surgery please advice me

    • profile image


      11 months ago

      My three-year-old Shih Tzu was and he about a month ago a couple weeks later her tits started filling up with milk she’s not pregnant I know what should I do?

    • alexadry profile imageAUTHOR

      Adrienne Janet Farricelli 

      13 months ago from USA

      Erica, I would get that discharge checked out by the vet to play it safe.

    • alexadry profile imageAUTHOR

      Adrienne Janet Farricelli 

      16 months ago from USA

      Naomi, your best bet is to have her see your vet, it can something as innocent as a skin tag to something more serious like a cancer. Too many variables that are not worth the risk of waiting. Best wishes.

    • profile image

      Naomi Clemts 

      16 months ago

      Can you please tell me what I can do for my female Chihuahua. She has some kind of a long head coming out of her nipple . She is in no pain she is eating normally and acts like she is fine there is some bruising a round the nipple but the bruising is starting to heal while the head is still in there. Can you tell me what I should do for her I want to take good care of her. Please help me. Thanks ,Naomi

    • profile image


      17 months ago

      I’m thinking my dog’s nipple disscharge is from a false pregnancy, but the thing is she hasn’t went into heat just yet. Her next heat should be coming up. I don’t see any signs of blood I’m the discharge.

    • profile image


      18 months ago

      I have a female yorkie,she has yellow crust on all her nipples...Have you heard of this???

    • alexadry profile imageAUTHOR

      Adrienne Janet Farricelli 

      18 months ago from USA

      Can be a sign of false pregnancy or mammary gland infection or tumor.

    • profile image


      18 months ago

      My 11 year old Chihuahua is having discharge from one of her nipples she’s never mated before does this mean she has cancer ?

    • profile image


      20 months ago

      my American bulldog has discharge coming from nipples but she aint pregnant wot does this mean

    • profile image


      20 months ago

      My pregnant retriever just has a green discharge from her nipple. Is this regular?

    • profile image


      21 months ago

      I'm a little worried, my almost 9 year old female unfixed Siberian/Malamute cross, I was petting her belly earlier and noticed what felt like her one breast was feeling full. I know she's not pregnant I'm very careful with her so she don't get pregnant with her age and she don't let the males near her anyway. But I was just checking on her now and it looks like a milky substance is coming out of that nipple. She has been tired a lot lately and a bit moody the last couple days but she seems to be in no pain, even when I put slight pressure on that breast earlier when I first noticed it she didn't squirm away or whimper or anything. Could someone please help explain... I can't afford to take her in to the vet right now.

    • alexadry profile imageAUTHOR

      Adrienne Janet Farricelli 

      21 months ago from USA

      Deborah, it may be a sign of a false pregnancy.

    • profile image


      21 months ago

      My dog. Never been with another dog but she has milk coming out of her breast what do that means

    • profile image


      22 months ago

      I still don't understand why my dog had white stuff come out I am like a kid learning.

      What should I do please I do not understand :)

    • profile image

      Latonya Aponte 

      24 months ago

      My dog has blood discharge from her nipple for about 2 months she seems to be in no pain.. Eating well still active.. Is she in pain what can I do at home.. no money for vet...

    • profile image


      2 years ago

      Omg,, thank u so much. I was freaking out that something was wrong with my little girl. Thank god it is just a false pregnancy. ;-)

    • DDE profile image

      Devika Primić 

      3 years ago from Dubrovnik, Croatia

      Interesting and most informative. I learned a lot from here on this topic.


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