Dog Swollen After Heat Symptoms

It’s common for female dogs to experience some swelling and enlargement of the vulva after going through a heat cycle. This swelling is usually temporary and caused by hormonal changes. In this article, we will cover the typical symptoms of post-heat swelling, explain the most common causes, and discuss when veterinary attention may be warranted. The main topics that will be addressed are normal vs abnormal swelling, common causes like vaginitis and trauma, and guidance on when to see the vet. By the end, dog owners should understand the typical swelling patterns after heat and how to monitor their dog’s health.

Normal Swelling

It is normal for a female dog’s vulva to experience some minor swelling after a heat cycle. The increased blood flow to the reproductive tract during estrus leads to slight swelling that may persist for 1-2 weeks after the cycle ends (source). This physiological response is due to the enlargement of the vulva and vaginal tissues during estrus to facilitate mating. As the estrogen levels decline post-estrus, the swelling gradually reduces as well. Minor swelling after heat may cause the vaginal area to appear slightly puffy or enlarged. As long as the dog is not showing signs of pain, discomfort, or abnormal discharge, this minor post-estrus swelling is not a cause for concern and will resolve on its own within a couple of weeks.

Abnormal Swelling

While some vulvar swelling after a heat cycle is normal, there are times when the swelling is considered abnormal and may indicate an underlying health issue (Source). Severe vulvar swelling that persists long after the heat cycle has ended often signals a problem. Other symptoms to watch for include:

  • Thick, smelly, or bloody vaginal discharge
  • Frequent licking, scratching, or scooting of the vulva area
  • Apparent pain or discomfort around the vulva
  • Loss of appetite, lethargy, or other signs of illness
  • Swelling that is lopsided or only affects one side of the vulva

If your dog exhibits any of these symptoms along with abnormal vulvar swelling, it’s important to have her examined by a veterinarian. Several conditions like vaginitis, uterine infection, or trauma can cause problematic swelling after a heat cycle.

Common Causes

There are several potential causes for abnormal swelling in a dog’s vaginal area after heat:


Vaginitis is inflammation of the vagina often caused by a bacterial infection. It can occur after heat as the vulva returns to a normal size. Symptoms include redness, swelling, discharge, and licking of the vulva. Vaginitis is easily treated with antibiotics prescribed by a vet (1).


Pyometra is an infection in the uterus causing pus and bacteria to build up. It is a serious and potentially fatal condition that can occur after heat. Symptoms include lethargy, vomiting, excessive thirst, swollen abdomen, and vaginal discharge. Emergency surgery is required to treat pyometra (2).

Allergic Reactions

Allergic reactions to grooming products, fabrics, grass, or other irritants can cause redness and swelling. Signs of an allergic reaction include itchiness, licking, and swelling of the vulva. Removing the source of irritation and applying a cold compress can provide relief (3).


Injuries from encounters with other dogs, falls, or excessive licking can physically damage the vaginal area leading to swelling. Preventing access to the vulva until it heals is important. Topical ointments, anti-inflammatories, or antibiotics may be prescribed by a vet.





Vaginitis is a common infection that causes inflammation of the vagina and vulva in female dogs. It often occurs after a heat cycle, when the vulva is swollen. Vaginitis is characterized by red, swollen tissue and abnormal discharge from the vulva.

The most common symptoms of vaginitis include vulvar swelling, vulvar discharge, licking of the vulva, and irritation or inflammation of the vulva. The discharge may be mucoid, purulent or bloody. Dogs with vaginitis often have an increased urgency to urinate as well.

Vaginitis can be caused by bacterial, viral or fungal infections. Bacterial vaginosis is most common, caused by bacteria like E. coli, Streptococcus, Staphylococcus, or Mycoplasma. Viral vaginitis may be seen after exposure to canine herpesvirus. Yeast infections are another cause of vaginitis in dogs.

To diagnose vaginitis, vets will take a swab of the discharge and examine it under a microscope. They may also culture the discharge to identify the causative organism. Blood tests and urinalysis may be done to check for other problems.

Treatment of vaginitis involves antibiotic medications to clear up the infection. Anti-fungals or antivirals may be prescribed depending on the cause. Vulvar swelling and irritation can be relieved with cold compresses. Most cases of vaginitis resolve within 7-10 days with proper treatment.


Pyometra is a bacterial infection of the uterus that can develop in dogs after heat. It occurs when bacteria enter the uterus and cause inflammation and pus buildup. Older, unspayed dogs are most at risk, but pyometra can occur in any dog after a heat cycle.

The main symptoms of pyometra are swelling of the abdomen and vulva, along with lethargy, vomiting, excessive thirst, and abnormal vaginal discharge. As pyometra progresses, dogs can develop fever, dehydration, septic shock, and even death if left untreated.

Pyometra is caused by hormonal changes during the heat cycle that make the uterine lining thick and ideal for bacterial growth. E. coli is the most common bacteria involved, entering the uterus during the heat cycle. The cervix remains tightly closed during infection, allowing pus and bacteria to accumulate.

Diagnosis is made through abdominal ultrasound, bloodwork, urinalysis, and bacterial cultures. Treatment involves emergency surgical removal of the infected uterus and ovaries, along with IV fluids and antibiotics. Dogs recover well with prompt treatment but pyometra can be fatal if the infection goes untreated and spreads systemically. Prevention involves spaying dogs before their first heat cycle.

Allergic Reactions

In some cases, swelling after a female dog’s heat cycle can be caused by an allergic reaction to mating. Some female dogs are allergic to proteins found in canine semen, which triggers an immune response after breeding occurs. According to the American Kennel Club (AKC), this condition is known as “bread allergy” or “stud dog allergy”.

The most common symptoms of an allergic reaction to breeding include swelling and irritation of the vulva and vagina. This swelling occurs within minutes to hours after mating. Other possible symptoms include hives, facial swelling, and respiratory distress in severe cases (WagWalking).

To diagnose this allergic reaction, a veterinarian will examine the dog’s symptoms and medical history. They may perform allergy testing on the semen to confirm. Treatment usually involves antihistamines, corticosteroids, and antibiotics if a secondary infection is present. Desensitization immunotherapy may also be recommended. Preventative measures can be taken such as using artificial insemination instead of direct natural breeding (VCA Hospitals).

In severe cases, dogs can experience anaphylaxis which requires immediate veterinary treatment. Signs of anaphylaxis include pale gums, weak pulse, collapse, vomiting, diarrhea and seizures. This is a medical emergency. Anaphylactic shock in dogs has a high mortality rate so fast action is imperative (VCA Hospitals).


One common cause of post-heat swelling in female dogs is trauma from mating or from the female dog excessively licking and biting at her vulva. The repetitive mating motions and licking/biting behavior can cause irritation, bruising, and inflammation of the external genital region, leading to painful swelling [1].

Trauma causes damage to the soft tissues including muscles, tendons and ligaments around the vulva. This type of injury is known as soft tissue trauma. It leads to inflammation, bleeding, and fluid buildup as the body responds to the trauma [2].

Applying cold compresses can help reduce pain, swelling, and inflammation during the initial stages after trauma. However, as healing progresses, gentle warm compresses may help improve blood flow and aid the healing process [3]. It’s important to minimize further trauma and allow time for the swelling and bruising to resolve.

If the swelling is severe or persists longer than expected, veterinary attention should be sought to check for underlying injuries or issues that may require treatment.

Other Causes

Some less common causes that could lead to abnormal swelling after heat in dogs include:

  • Tumors – Both malignant and benign tumors in the reproductive tract can cause swelling. Tumors should be evaluated by a veterinarian.
  • Urinary tract infection – An infection in the urinary tract can spread and cause inflammation and swelling of the vulva. Urine cultures and antibiotics may be needed.
  • Skin infection – Bacterial or fungal skin infections around the vulva area can lead to irritation and swelling. Topical medication may be prescribed.
  • Trauma – Injuries to the vulva from bites, scratches, burns, etc. can result in pain and inflammation.
  • Allergies – Allergic reactions to grooming products, chemicals, or other irritants could trigger vulvar swelling.

Swelling from any of these causes warrants a veterinary exam to diagnose the specific problem and provide appropriate treatment.

When to See the Vet

Some swelling after a heat cycle is normal, but there are some signs that may indicate a more serious issue requiring veterinary attention:

If any of these signs are present, take your dog to the veterinarian right away for evaluation and treatment. Prompt medical care can help prevent complications and relieve discomfort.

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