Female Dogs In Heat: What They Look Like [Pictures & Vet Info]

This article was updated on October 5th, 2026

You may be prepared for the bleeding that will accompany your dog’s first heat cycle, but there are other bodily changes that might come as a surprise. When a female dog is “in heat” (estrus) and receptive to mating, there are multiple surges and drops in her hormone levels, which have varying effects on her body.

In this article, you will find pictures of female dogs in heat to help you understand what is normal, and when you might need to call your vet.

A swollen vulva is often one of the first signs that a dog is in heat

When your dog experiences their first heat cycle, between six and eighteen months of age, you may notice a dramatic swelling of the vulva. Most of the time, it is a normal finding, caused by the effects of estrogen on your dog’s reproductive tract. This picture shows the swollen vulva of a dog in heat:

The vulva will remain enlarged throughout the dog’s fertile period, and then it will gradually decrease in size. It’s important to note, however, that your dog’s vulva may never return to the size that it was before her first heat cycle.

Dogs that have had one or more heat cycles will often have a vulva that remains permanently larger than that of dogs spayed before their first heat.

What a female dog looks like when in heat [3 pictures]

In these pictures below, you can see the appearance of a slightly swollen canine vulva, accompanied by a small amount of bloody vaginal discharge:

Signs your dog may be in heat:

Some of the signs are subtle or behavioral in nature. However, there are also clear visual cues that indicate a dog is in heat:

• Swelling or enlargement of the vulva
• Bloody or blood-tinged discharge from the vulva
• Urinating more often than usual
• Licking at the vulva more often than usual
• Increased mounting/humping behavior
• Increase in anxious behavior
• Roaming or increased interest in male dogs

The only way to prevent heat-related vulvar swelling is to have your dog spayed.

As long as your dog is experiencing heat cycles and is not spayed, you will continue to see episodes of vulvar swelling.

Spaying can also help your dog live a longer, healthier life

Spaying your dog can have the following medical benefits:

• Spaying your dog while they are relatively young can markedly decrease your dog’s risk of mammary (breast) cancer, a common health threat in dogs.
• Spaying your dog will prevent uterine cancer.

Spaying your female dog before her first heat provides the best protection against these diseases.

Call your vet if your dog is demonstrating extreme swelling or swelling that is occurring while they are NOT in heat

Vulvar swelling is normal when a dog is in heat. If you know that your dog is in heat and their vulva is mildly to moderately swollen, monitoring your dog at home is a reasonable option.

However, if your dog is demonstrating extreme swelling of the vulva or swelling that is occurring while they are not in heat, you should seek veterinary care. Your veterinarian will perform a thorough physical examination and diagnostic tests to determine the cause of your dog’s vulvar swelling and recommended treatments.

Medical issues causing vulvar swelling [issues to be aware of]

While swelling of the vulva is a common sign of heat, there are also medical conditions that may cause vulvar swelling. It’s important to be able to distinguish between heat and these potentially-serious conditions:

Top causes of abnormal swelling

Click here to see a picture showing a degree of swelling that may be normal in some dogs, but is likely abnormal or problematic swelling in most dogs. Let’s review the most common causes:

1. Vaginitis

While a dog’s heat cycle is accompanied by vulvar swelling and bloody discharge, you may also notice inflammation of the vulva and a purulent (pus-filled) discharge if your dog has vaginitis. This condition is common in young puppies, but can also occur in adult female dogs. Vaginitis may also be accompanied by redness around the vulva.

There are a variety of recommended treatments for vaginitis in dogs, depending on your dog’s overall condition and the severity of the vaginitis. See your veterinarian if you suspect that your dog may have vaginitis.

2. Vaginal hyperplasia

Vaginal hyperplasia is another condition that can cause swelling in the area of the vulva. In this condition, fluid-filled vaginal tissue prolapses from the vulva and is visible outside the body. This condition is most common in intact dogs and is associated with the effects of estrogen.

This picture may be shocking to some readers: click here to view.

If your dog has vaginal hyperplasia, they need veterinary care to prevent infection and injury to their prolapsed vaginal tissues. Your veterinarian will also likely recommend spaying your dog, to prevent future episodes of vaginal hyperplasia.

In some cases, vaginal hyperplasia can block a dog’s ability to pass urine. This is a life-threatening emergency and requires emergency veterinary care.

3. Rectal prolapse

In contrast to vaginal prolapse, rectal prolapse can affect both male and female dogs. In this condition, usually caused by gastrointestinal issues and/or excessive straining to defecate, a small amount of tissue prolapses from the rectum. Rectal prolapse is a medical emergency. Seek veterinary care immediately if you suspect rectal prolapse. Learn about about prolapse in dogs.

5 tips to help a dog in heat

Your dog’s heat cycle can be stressful for both you and your dog. Consider the following steps to reduce your dog’s stress:

1. Walk your dog during quiet times of the day.

Male dogs will be attracted to your dog’s scent. Walk her when fewer dogs will be outside.

2. Bathe your dog to control odors.

Most dogs will groom themselves to remove blood and vaginal discharge. Bathing your dog can help minimizing the amount of self-grooming that she needs to do

3. Distract your dog with play.

If your dog appears restless or anxious, interactive play can help distract her from her heat cycle.

4. Keep your dog on-leash and closely supervised.

In order to prevent unwanted mating, it’s important not to allow your dog outside unattended.

5. Have your dog spayed.

If you do not plan to breed your dog, you should have her spayed to prevent further heat cycles and help increase chances that your dog lives a happy & long life.

Interesting questions about the heat cycle

How often do dogs go into heat?

Most dogs go into heat every six months or twice yearly. However, some dogs may have as few as one heat cycle per year, while other dogs may have as many as three heat cycles in a year.

Is my dog in pain when in heat?

Being in heat isn’t painful, but it can cause some discomfort or restlessness. If your dog appears painful, consult your veterinarian. 

What do I do if my female dog’s vulva is swollen but she is not in heat?

If your dog’s vulva is swollen and you know that she is not in heat, contact your veterinarian. Your veterinarian will perform a physical examination and laboratory tests to rule out infections, tumors, and other problematic causes of vulvar swelling.

Do female dogs go through a menopause stage?

Dogs do not experience menopause in the way that we see in humans. A dog’s heat cycles may become less frequent with age, but they do not typically stop completely. Most dogs can become pregnant throughout their lifespan.