My Dog's Nipple is Leaking - Types and Causes of Discharge

If you are worrying about discharge from your dog's nipple, one of the first things to consider is their sex. Both female and male dogs have nipples, but only the females are strictly functional. This is because they use them to nurse their young after birth and before they are weaned onto solid food. Male dogs have nipples which are essentially vestigial. All mammal embryos begin as female, it is only later on that maleness develops^[1]. Male dog nipples are a leftover element of this experience.

With female dogs, there are different considerations to make if you see discharge from their nipple. The most important factor is pregnancy. Some people may think that a dog will only lactate after they have given birth. However, pregnant female dogs can start the lactation process a few days or even a week before they give birth to their litter. In these cases, the discharge will be of a clear or milky consistency.

The cause of milk production, is a neuropeptide known as oxytocin which “is produced in the paraventricular and supraoptic nuclei in the hypothalamus and is known to stimulate milk ejection during breastfeeding and uterine contractions during labor”^[2]. If the dog starts releasing oxytocin earlier, then milk production may begin earlier also. We should know not to touch or squeeze the lactating dog's nipples. This is because doing so could interrupt the process or even cause infection which can be passed on to the weaning puppies.

While we might think of discharge due to lactation as only being white in color, it is also normal to see a slightly yellow discharge occurring before birth. With any type of nipple leaking in female dogs, it is only problematic when the dog is not pregnant, nor have they recently given birth.

IN cases where the female dog is not pregnant, but they are showing signs as if they were, we may be encountering a false pregnancy. Clinical pseudopregnancy in dogs is a “syndrome observed in non-pregnant dogs and is characterized by clinical signs such as nesting, weight gain, mammary enlargement and lactation”[3].

If we see that our female dog looks as if she is lactating or there is a white or yellowish discharge from their nipples, we need to know if she is pregnant. If she has been sterilized and has had no contact with a male dog, then it is likely, but we will still need to take them to the vet for an accurate diagnosis. The same study quoted above claims that canine pseudopregnancy (sometimes known as false pregnancy) could be caused by higher concentrations of prolactin (the protein related to milk production), but also discusses the role of progesterone in prolactin production.

Canine pseudopregnancy occurs between 6 and 12 weeks after a dog's estrous cycle where these hormone levels rise. Physical and behavioral symptoms of a dog with pseudopregnancy include:

• Nesting (finding a comfortable spot as if she were to raise pups)
• Digging
• Weight gain or anorexia
• Mammary gland enlargement
• Aggression
• Over-protectiveness
• Excessive licking
• Lactation
• Mothering of objects

The last symptom on this list usually involves a toy. The dog will mother it as if they were their own offspring and take it somewhere to look after them. Their aggression might come when you try to take this object away as the dog can defend it as if it were their own. Some female dogs might go into a state of depression during a pseudopregnancy.

Physically, the dog's abdomen may enlarge and, in rarer cases, vomiting and diarrhea might occur. Again, we should not manipulate the breasts as it can lead to infection and other problems. Mastitis (something we'll look into further below) can occur which results in inflammation and can be painful. The symptoms of pseudopregnancy in dogs usually leave on their own accord. However, it can come back after another estrus cycle ends. In these cases, it is highly recommend the dog is sterilized.

As we stated above, it is possible for some yellowish discharge to occur prior to lactation in female dogs. However, there are other types of yellow discharge which might be more concerning. If it occurs shortly after the mother has given birth, it could be a case of acute septic mastitis. This is because the puppies can agitate the nipples during suckling and allows bacteria to enter the nipple.

Affected female dogs will have a fever, become depressed and may refuse food. Infected and swollen breasts are usually the ones closest to the groin area. They may become painful and take on a bluish color. The yellow discharge is due to the infection. Hygiene is also an important factor as dogs in unclean environments may have an increased risk of developing bacterial infection. The dog's milk may contain a little blood or take on a yellowish color. However, it is possible for the breasts to be enlarged, but the milk is still a white color.

Dogs which have just given birth might also develop mastitis due to galactostasis. This is the “overload of the mammary gland with milk that is seen before the parturition [giving birth] or shortly afterwards”^[4]. Due to the enlargement, the milk is unable to be let-down and the result is mastitis. Other cause of mastitis in dogs include mammary gland tumors and mammary gland hyperplasia (the latter being a kind of benign tumor).

Treatment of mastitis will depend on the cause. In case of infection, antibiotics will normally be prescribed. However, if the cause is galactostasis then the first course of treatment should be to prohibit feeding. In terms of tumors, whether malignant or benign, surgery will most likely be undertaken. If the mastitis is left untreated, the result could be gangrene or even death.

If your dog is leaking blood from their nipples, it won't always look red like fresh blood. Instead, the color might be coffee brown or similar. As we stated above, it is possible that mastitis will be accompanied by blood leakage. However, there are other causes which need to be considered.

If your dog has a dark brown or reddish liquid leaking from their nipple, but it is not fresh, it may be due to the presence of a tumor. This can occur in one or several of the dog's breasts. Both cancerous and non-cancerous tumors can cause lumps to occur. It will require an examination and tests by a vet to determine if a lump is cancerous.

With breast cancer in dogs, the main symptom is a painless mass that sometimes causes ulceration of the skin and bleeding. This type of tumor runs the risk of metastasis to other parts of the body, especially the lungs. The treatment requires surgery, although it will depend on how far the disease has progressed. There is a much higher breast cancer risk in unsterilized dogs, only one of the important reasons for sterilization. We should also pay attention to any changes in our dog's breast tissue, especially in dogs over six years of age. If we detect any leakage, inflammation, pain or hard lumps, we need to take our dog to the veterinarian.

Blood leaking from a dog's nipple might have a less life threatening reason. Abscesses can occur when the dog has an injury or a foreign body has entered the skin. These may have a mixture of blood and/or yellowish or green discharge. The abscess grows as pus becomes trapped underneath. The abscess may leave on its own accord, but it does rub the risk of further infection or becoming septic. For this reason, it is important to go to the vet for treatment.

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.

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