Why Do Female Dogs Breasts Swell?

Dogs are mammals, and for this reason, female dogs have mammary glands that produce milk to feed their puppies. The milk flows out through the dog’s nipples.

Sometimes, a female dog’s nipples may swell. But what causes the nipples to swell? The nipples may become enlarged and red as if they’re producing milk for puppies. However, the swelling may be caused by other conditions, too.

We’ve put together some information about what may cause a female dog’s nipples to swell. Let’s get started!

Reasons a Female Dog’s Nipples May Swell

There are four main causes of swollen nipples in female dogs, including the following conditions.

1. Pregnancy

When a female dog is pregnant, her nipples may begin to swell, usually becoming engorged, especially just before she gives birth. The dog’s gestation period is usually between 58 to 68 days (depending on the breed). During this time, the nipples will gradually become more swollen.

After she gives birth, the dog’s nipples remain swollen. This is caused by producing milk for her puppies and from the puppies’ suckling. The nipples may stay swollen for a short time even after the puppies have been weaned.

2. Heat Cycles

Normal heat cycles can also cause a female dog’s nipples to swell. This is a common condition in female dogs that have not been spayed. Female dogs go through four cycles of heat (estrus), lasting about 21 days.

During heat, the mammary glands may swell a little bit. They may not reduce in size until the last stages of the heat cycle are finished. This is normal and nothing to be worried about.

3. Mastitis

Mastitis is another common cause of swollen nipples in female dogs that have recently given birth. The nipples are normally swollen at this time due to producing milk and the puppies’ nursing.

However, there’s a condition called mastitis that may develop at this time. The dog’s nipples become infected during nursing. If this happens, the nipples become more swollen and feel painful. The condition can also cause the dog’s milk to become toxic. This condition usually appears within the first two weeks after giving birth.

4. Mammary Gland Tumor

Mammary gland tumors are another common cause for a female dog’s nipples to swell. This is similar to breast cancer in humans. The tumor in the mammary gland most often affects female dogs. The mass grows around the dog’s nipples, and the color can vary from red to purple. The tissue may also feel hard or soft and may develop abscesses.

Mammary tumors may be benign or malignant. Benign tumors usually grow slowly, while malignant tumors usually grow quickly and have an irregular shape.

What to Do If Your Female Dog’s Nipples are Swollen

If your female dog’s nipples seem to be larger and more swollen than normal, then it’s best to call the vet. The vet can determine the underlying cause and treat it. This is imperative, especially if your dog has cancer. The sooner she has been diagnosed and treated the better!