Female dogs’ nipples can become swollen for a variety of reasons. The main causes of nipple swelling in female dogs include pseudopregnancy, mammary gland hyperplasia, mastitis, mammary tumors, breast cancer, injuries, and allergies. This article will provide an overview of the potential causes of nipple swelling in female dogs, information on diagnosing the underlying cause, and available treatment options.
Pseudopregnancy
Pseudopregnancy, also known as false pregnancy, is caused by hormonal changes after a female dog goes into heat. Even though the dog is not actually pregnant, her body shows the same signs and symptoms. According to [vcahospitals.com/know-your-pet/false-pregnancy-or-pseudopregnancy-in-dogs], the most common signs of pseudopregnancy include mammary gland enlargement with or without milk production.
The hormones that prepare a dog’s body for pregnancy do not dissipate after her heat cycle ends. As a result, her body mimics the signs of pregnancy even though conception did not occur. One of the most noticeable symptoms of pseudopregnancy is enlarged nipples. According to [petmd.com/dog/conditions/reproductive/c_dg_false_pregnancy], the mammary glands and nipples enlarge evenly during pseudopregnancy, and the dog may even produce some milk.
While pseudopregnancy is not dangerous on its own, the hormonal changes and nipple swelling can cause discomfort for the dog. Pet owners should monitor for signs of mastitis or mammary tumors if the nipple swelling persists. Treatment usually involves addressing the underlying hormonal causes.
Mammary Gland Hyperplasia
Mammary gland hyperplasia is a noncancerous growth of tissue in the mammary glands that can cause swelling in the nipples. It occurs when there is an abnormal increase in the number of normal cells in the mammary tissue, resulting in enlargement of the mammary glands (1).
Hyperplasia is stimulated by hormones, usually estrogen, progesterone and prolactin. Intact female dogs that are not spayed are at a higher risk since their hormones fluctuate during the estrus cycle. However, hyperplasia can also occur in spayed dogs if they have residual ovarian tissue producing hormones after the surgery (2).
With mammary gland hyperplasia, the nipples and mammary glands become swollen, enlarged and firm. The swelling is generally symmetrical, affecting all glands and nipples at the same time. It may feel like small masses or nodules in the glands. Hyperplasia does not usually cause any pain, irritation, nipple discharge or skin changes.
While hyperplasia itself is benign, the overgrowth of cells increases the risk of developing mammary tumors in the future. For this reason, surgical removal of the abnormal tissue may be recommended. Spaying the dog is also advised to stop the hormonal stimulation of the mammary glands (3).
Mastitis
Mastitis is a common cause of nipple swelling in female dogs and refers to an infection of the mammary glands or breast tissue.
It is most commonly caused by a bacterial infection, often from bacteria that enter through openings in the skin or ducts of the mammary glands. The most common bacteria implicated in canine mastitis are Staphylococcus, Streptococcus, and Escherichia coli.
The symptoms of mastitis include redness, swelling, pain, and warmth in the breasts or nipples. There may also be a watery or pus-like discharge. Mastitis most often occurs in lactating female dogs, as the distention of the mammary glands during nursing and milk stasis provides an opportunity for bacteria to enter and infect the tissue. However, it can occur in non-lactating dogs as well.
Treatment of mastitis involves antibiotic therapy to clear the bacterial infection. Anti-inflammatories are also often prescribed to help manage pain and swelling. In some cases, surgical drainage or removal of infected mammary tissue may be necessary. Prompt veterinary care is important, as mastitis can quickly become a systemic infection if left untreated.
To help prevent mastitis, keeping the mammary glands clean and avoiding trauma to the nipples is recommended. Gentle massage to express milk and keep ducts clear may also help prevent milk stasis. Monitoring for any signs of redness, swelling, or pain is advised in lactating dogs.
For more information, see:
https://vcahospitals.com/know-your-pet/mastitis-in-dogs
Mammary Tumors
Mammary tumors are abnormal masses of tissue that develop in the mammary glands of female dogs (1). Both malignant (cancerous) and benign (non-cancerous) tumors can develop in the mammary glands. Benign mammary tumors are the most common type of mammary tumors in dogs. These tumors tend to be small, firm nodules that involve only one or two mammary glands. They typically do not spread to other areas of the body. However, they can still negatively impact a dog’s health if left untreated.
Mammary tumors often cause swelling and enlargement of the nipple and mammary gland region. The swelling may feels like a small mass or lump located under the skin. Mammary tumors can also lead to discharge from the nipple. The discharge may be milky, serous, or bloody. Some dogs will lick at the nipple excessively due to the discharge. If a mammary tumor is suspected, examination and testing by a veterinarian is required to confirm the diagnosis and determine the appropriate treatment.
Breast Cancer
One potential cause of swollen nipples in female dogs is malignant mammary tumors, also known as breast cancer. Breast cancer in dogs begins when normal cells in the mammary glands transform into abnormal cells that grow and multiply uncontrollably. These cancerous cells can eventually form into tumors in the mammary glands.
As the tumors grow, they can ulcerate and spread to the skin surrounding the nipple, causing it to become swollen, inflamed, or irritated. Breast cancer is the most common type of tumor in unspayed female dogs. According to the Blue Cross, around 50% of breast tumors in dogs are cancerous. Malignant mammary tumors are able to spread via the lymphatic system to lymph nodes and other organs. Therefore, swollen nipples may potentially be an early clinical sign of breast cancer in some cases.
It’s important to have mammary masses evaluated by a veterinarian to determine if they are benign or malignant. Treatment for mammary cancer involves surgery to remove the tumors. The prognosis depends on the size and location of the tumors, whether the cancer has spread, and the dog’s overall health. However, mammary cancer often carries a fair to guarded prognosis compared to other cancers. Catching it early is key, so investigating any nipple swelling is advised.
Sources:
https://www.bluecross.org.uk/advice/dog/health-and-injuries/breast-cancer-in-dogs
Injuries
Trauma from scratches, bites, or other injuries can also cause a female dog’s nipples to swell. Getting scratched or bitten on the nipples and mammary glands can result in tissue damage and bruising, leading to swelling and inflammation.
The sensitive mammary tissues are prone to injuries during nursing and weaning, as puppies may scratch or bite the area. Mammary injuries may also occur during mating. In addition, activities like running through brambles or thick brush could scratch or tear the delicate skin of the nipples and lead to swelling.
Signs of nipple or mammary injury include bruising, cuts, bleeding, and significant swelling of the breast and teat. The swollen, damaged tissue may appear red, inflamed, or filled with fluid. Medical treatment is required to prevent infection and allow proper healing.
Allergies
Allergies are a common cause of swollen nipples in female dogs. Allergic reactions to things like food, medications, insect bites, pollen, or other environmental allergens can cause hives, swelling, redness, and itching of the nipples and mammary glands.
Dogs can develop allergies to proteins in food like beef, dairy, chicken, lamb, fish, eggs, corn, wheat, and soy. Food allergies result in itchy skin and ears, gastrointestinal signs like vomiting and diarrhea, and swelling of the face, paws, underarms, and mammary glands.
Medications like vaccines, antibiotics, heartworm preventatives, and flea/tick treatments can also provoke allergic reactions in some dogs. These reactions usually occur within hours or days of exposure to the medication.
Bites from insects like fleas, mosquitoes, spiders, or bees can cause isolated swelling and hives on the skin. The nipples and underside are common sites for allergic reactions from insect bites in dogs.
Treatment involves removing the allergen and providing symptomatic relief with antihistamines, steroids, or oatmeal baths. Identifying and avoiding the causative allergen is key to preventing recurrent reactions.
If nipple swelling is accompanied by trouble breathing, vomiting, or lethargy, emergency vet care is needed as these can be signs of anaphylaxis.
(Source: https://vethelpdirect.com/ask-a-vet/topic/swollen-nipple-and-red-itchy-skin/)
Diagnosis
To diagnose the cause of swollen nipples in female dogs, the vet will first perform a physical exam and take the dog’s medical history. They will look for abnormalities and feel the mammary glands, nipples, and lymph nodes for signs of inflammation, pain, or masses.
The vet may recommend bloodwork like a complete blood count, biochemistry profile, and urinalysis to check for signs of infection or other systemic issues. Imaging tests like x-rays, ultrasounds, or mammograms can allow the vet to visualize the internal mammary tissue and look for masses or abnormalities.
If a tumor or mass is detected, the vet will likely recommend biopsying the abnormal tissue. This involves surgically removing all or part of the mass and sending it for histopathology, which can determine if it is benign or malignant. Biopsies are crucial for confirming a diagnosis of mammary tumors or breast cancer.
With the information from diagnostic testing, the vet can determine the likely cause of the nipple swelling, such as pseudopregnancy, mastitis, benign masses, or mammary cancer. This will inform the proper treatment plan.
Treatment
The treatment for swollen dog nipples depends on the underlying cause. If there is an infection like mastitis, antibiotics will likely be prescribed to clear up the infection. Pain medication may also be given to relieve discomfort. In severe cases of mastitis, the infected mammary gland may need to be removed surgically.
For cases of mammary gland hyperplasia or benign mammary tumors, surgery is often recommended to remove the abnormal tissue. Anti-inflammatory medication can help reduce swelling. If the dog is experiencing a false pregnancy, hormones like cabergoline may be prescribed to interrupt the pseudopregnancy cycle.
Regardless of the cause, keeping the area clean and preventing further injury is important. Applying warm compresses to swollen dog nipples can help draw out infection and reduce swelling. Allowing puppies to continue nursing can also help clear mastitis infections. While home remedies may provide some relief, veterinary attention is crucial for proper diagnosis and treatment of swollen dog nipples.
