Why Are My Dog’s Nipples Enlarged After Heat?

correct answerThe Short Answer is:

Because your dog's body still contains a large amount of progesterone hormone its nipples enlarge after heat. After the first heat the mammary glands swell due to this high hormone level.

In this research you will know the answer to the query “Why Are My Dogs Nipples Enlarged After Heat?“.

Getting a dog is like entering new territory and nothing is more mysterious than your pets reproductive cycle and everything that goes along with it.

In the event that your pet hasnot been spayed yet you may have been told to expect her to go into heat.

Veterinarians sometimes recommend letting a buck go through a first heat cycle before spaying.

Even though she is no longer pregnant her nipples are still enlarged. Why is this so? Are they dangerous? Are there any solutions?

You have nothing to worry about. You’ll be fine. Its a natural reaction.

Nevertheless you need to keep an eye on your dog in case those enlarged nipples indicate a health problem.

Now lets take a quick look at the main points of a dogs heat cycle and what dogs nipples enlarged after heat cycle may mean.

What are the stages of a dog’s heat cycle?

Lets start at the beginning.

At the age of puberty a female dog experiences her first heat cycle. This depends on the breed of the dog.

The average age at which a bitch goes into heat for the first time is six months but smaller breeds reach sexual maturity much earlier.

However females of large breeds might not reach puberty until they are 18-24 months old.

There are four stages in a dogs heat cycle. Pet owners are interested in the first two stages which are called proestrus and estrus.

proestrus During proestrus the dogs body prepares for breeding and there are few signs that may alert the owner to what is happening.

During this time estrogen levels rise but the female is not yet interested in males. A pet might be a bit more agitated during this stage which can last up to nine days.

estrus As a female dog becomes fertile she actively searches for a male partner during the estrus period.

The dogs body begins preparing for a possible pregnancy by decreasing estrogen levels and increasing progesterone levels.

Your first observation might be the bloody discharge.

Comparing this stage to human physiology can be confusing. When it comes to dogs things are completely different from when it comes to women.

It will be bloody at first but it will become more watery over time.

At this point the dog is ready for breeding and the eggs have been released.

This is also the time when you will notice an enlarged nipple as well as swelling of the vulva and mammary glands.

You’ll notice shes peeing more often and marking her territory. Her urine contains pheromones that tell male dogs shes seeking a mate.

Estrus typically lasts between nine and fourteen days.

Diestrus occurs when your dog is no longer in heat.

She still has high progesterone levels but she has stopped mating and no longer welcomes male attention.

Despite her body still being full of progesterone the dog will still have an enlarged vulva and nipples.

There is no need to worry about your dogs enlarged nipples during this stage which can last for up to two months. Once the swelling subsides your dog will be back to normal.

Anestrus occurs during the time when the females hormone levels have returned to normal and she does not care about the male dog at all.

Do dog nipples shrink after spaying and will they return to their original size? It will take about a month for her vulva and nipples to return to their original sizes. Experts say your dogs nipples would not shrink back to their original size after entering puberty.

In females anestrus lasts for 2-3 months before she goes into heat again.

Its not uncommon for small breeds to go through two or three heat cycles in a calendar year.

What is a false pregnancy?

After heat your dog might think she is pregnant which can lead to serious enlargement of the nipples.

Women can experience false pregnancy regardless of whether they have mated or not.

The nipples of your dog will look swollen and you may notice your dog is gaining weight. Her milk production might even increase although thats not always the case.

As the dog prepares to give birth to an imaginary letter you’ll also observe a distinct nesting behavior.

Some females will have fake births and you’ll see her straining to give birth to those nonexistent puppies. Additionally she might show protective behavior towards other puppies or kittens.

False pregnancies usually resolve themselves after a few weeks so you have very little choice but to let her be.

Especially if she starts producing milk you should check her nipples periodically.

An inflamed nipple and the underlying tissue can be painful.

Galactosis is the accumulation of milk in the mammary glands after a false pregnancy or during the weaning period for a buck that has had puppies.

Speak to your vet if she is showing signs of discomfort.

In addition to giving your dog medication to reduce inflammation the vet may also show you how to apply ice packs to help relieve pain.

How would it be if?

Its important not to assume that your dog is going through a false pregnancy just because you do not think shes mated.

Unless you have been watching her through her whole estrus stage you wouldnot know that.

During the time you thought she was sleeping under her favorite tree in the backyard she might have had some fun.

Your fence might not stop a male dog from getting near a bitch in heat.

Its important to know that a dogs nipples become enlarged and darker during a real pregnancy.

They turn discolored towards the end of pregnancy and there will be a milky discharge.

What is mastitis?

Usually associated with nursing dogs mastitis is another common condition.

It is possible to get an infection from biting or tearing at the puppies’ nipples. Breastfeeding dogs are not the only ones who can suffer from mastitis.

An infection of the mammary tissue can also occur during a false pregnancy and in some cases even male dogs can contract it.

There may also be a reddish discharge if your nipples are very swollen and painful.

You should take your dog to the vet because she will need antibiotics to treat the infection.

Surgery may be necessary to remove one or more mammary glands in extreme cases.

Why does my dog have lumps under her nipples? Lumps Under Dogs Nipples After First Heat

Its completely normal for an intact dogs nipples to swell during her female cycle.

A lump beneath the dogs nipples however will cause the owner to flee in a panic.

Cancer is the first thing that comes to mind when you see a tumor.

It is not always the case however.

Do dogs nipples swell during a heat cycle? During your dogs heat cycle it is normal for certain lumps or masses to appear.

They result from high progesterone levels but the good news is that they will disappear once hormone levels return to normal.

Tumors that are benign or malignant

A lump on the other hand is not something you want to ignore because it could be malignant.

They usually affect the fourth and fifth nipples those closest to the groin and can reach a diameter of 2 to 3cm.

Taking your dog to the veterinarian is necessary if the lumps do not disappear after the dog has stopped being in heat.

During a Fine Needle Aspiration (FNA) or biopsy a doctor will extract cells from the lump to see if its a benign or malignant tumor.

It is possible for a dog to have a benign tumor and a malignant tumor at the same time.

Moreover a benign tumor cannot be predicted how it will behave over time. Over time some tumors may remain unchanged while others may become malignant.

In the event that your dog has any type of mammary tumor the vet will likely advise that it be removed just to be safe.

In spayed dogs whose hormone levels are not altered malignant tumors are rare.

According to experts progesterone plays an important role in the abnormal proliferation of breast tissue.

A vet will probably recommend spaying your intact dog when a tumor whether benign or malignant is discovered as well as removing the growth.


Swollen nipples in female dogs are quite normal once they are in season.

It is not uncommon for her nipples to appear enlarged for several weeks after a season that lasts an average of 21 days.

Her nipples should return to normal or almost normal once the progesterone levels in her body start dropping since they would not return to the size they were before the first heat cycle.

Make sure you take your pet to the vet if she exhibits any signs of inflammation or infection.

If you find a suspicious lump near your dogs nipple have it checked out as soon as possible. 

If you want to read more about dog daily tips read here: Dog Daily Tips and Tricks.

Why Are My Dog’s Nipples Enlarged After Heat? (Watch Video)

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