Do Dogs Get Sick After Heat Cycle?

A heat cycle, also known as an estrous cycle, is a normal physiological process in intact (not spayed) female dogs where their reproductive system prepares for pregnancy. The heat cycle occurs roughly twice a year, although the interval can vary between breeds. During this time, estrogen levels rise and the dog’s body goes through changes to prepare for potential mating and pregnancy (

After a heat cycle, dog owners may notice some changes in their dog’s behavior and health. Some dogs can experience mild illnesses or behavior changes following their heat. This article will explore the topic of dogs potentially getting sick after their heat cycle and cover the common illnesses, preventative measures, signs of illness, and treatments.

Physical Changes

Dogs experience several physical changes during a heat cycle. The most noticeable change is swelling of the vulva. According to PetMD, the vulva begins to swell slightly around the onset of proestrus and continues swelling throughout the cycle. The swelling is accompanied by bloody vaginal discharge starting a week or two after the vulva begins to enlarge. The bloody discharge can range from a light pink color to a dark rusty red. PetMD also notes that some dogs experience a change in the vulva’s color, usually becoming darker or taking on a strawberry-like tone.

According to The Spruce Pets, vaginal discharge usually lasts around 9-10 days but can persist for up to 3 weeks or longer in some dogs. The discharge may start out bloody and then become watery and straw-colored near the end of estrus. The texture and amount of discharge can vary not just from dog to dog, but even between cycles for the same dog. The Spruce Pets emphasizes tracking the vaginal discharge closely, as it signals when a dog is most fertile for breeding purposes.

In summary, the most significant physical changes female dogs undergo during a heat cycle are swelling of the external vulva and bloody vaginal discharge. Carefully monitoring these physical symptoms helps owners identify where their dog is in her cycle.

Behavioral Changes

When a dog enters her heat cycle, there are common behavioral changes you may notice such as increased nervousness, restlessness, and moodiness. According to Preventive Vet (, your dog may become more alert or easily startled during her heat. She may also become more anxious or seem to be “on edge.”

Restlessness is another common behavioral change, and your dog may pace or seem unable to get comfortable. She may follow you more closely during her heat. Dogs in heat tend to be moodier as well. According to Four Paws (, your dog may become short-tempered and irritable during this time.

These behavioral changes are caused by shifts in your dog’s hormones during her heat cycle. Being aware of these common changes can help you provide any extra attention or care your dog may need to remain comfortable and happy during this time.

After Heat Changes

After a dog’s heat cycle ends, there are some common physical changes that may occur. The swollen vulva will begin to shrink back down to its normal size. The vaginal discharge changes from bloody to watery and light pink or straw-colored. This discharge called “serosanguineous” discharge can persist for weeks or months after heat.

Another very common change is enlargement of the nipples. According to Preventive Vet, the breasts enlarge and nipples become more prominent. This is in preparation for potential pregnancy and milk production. The nipples will remain enlarged for several weeks after heat. Though the breasts may feel firmer, any significant swelling could indicate a medical issue that requires veterinary attention.

Most of these changes are normal following a heat cycle. However, if you notice anything unusual like foul-smelling discharge, signs of illness, or abnormal swelling, consult your veterinarian.

Potential Illnesses

There are a few illnesses that dogs can develop following a heat cycle due to changes in their hormones and reproductive systems. One of the most dangerous is pyometra, which is an infection in the uterus that occurs when progesterone levels remain high after estrus (heat). As described by VCA Hospitals, “Following estrus (heat), progesterone levels remain elevated for two to three months in the dog, maintaining a condition in which the lining of the uterus is thickened and suitable for embryo implantation.” (1) This thickened uterine lining is prone to bacterial infection, often leading to pus filling the uterus – hence the name pyometra which means “pus uterus.”

If pyometra develops, dogs may show symptoms like lethargy, vomiting, increased thirst, fever, and abdominal swelling or discharge. This is a medical emergency requiring prompt veterinary treatment, usually including surgery, antibiotics, and IV fluids. Without treatment, pyometra can be fatal within days. (2) Other potential illnesses after a heat cycle include mastitis (breast infection) which leads to swollen, painful mammary glands, and urinary tract infections which cause symptoms like frequent urination, bloody urine, and abdominal pain.



Preventing Illness

There are several things you can do to help prevent illness after your dog’s heat cycle:

Keep the dog clean. Gently wipe the vaginal area with unscented baby wipes daily to remove any discharge and prevent infection. Do not let the dog swim in public waters or share toys with other dogs during this time.

Visit the vet promptly. Take the dog to the vet within 2 weeks after the heat cycle ends for an exam. The vet can prescribe antibiotics as a preventative measure against uterine infections like pyometra (Source).

Spay your dog. The best way to prevent deadly uterine infections is to spay your dog before her first heat cycle, ideally around 6 months old (Source). Spaying removes the uterus and ovaries, eliminating the risk of pyometra.

Keep a close eye. Monitor your dog closely for signs of illness like lethargy, loss of appetite, vomiting, or vaginal discharge. Seek prompt veterinary care if you notice anything abnormal after the heat cycle.

Signs of Illness

After a heat cycle, it’s important for dog owners to monitor their dog closely for any signs of illness. Some concerning signs to look out for include:

Lethargy: Dogs who are normally energetic may suddenly become very tired and inactive. According to the VCA, lethargy is one of the most common symptoms of pyometra (

Vomiting: Persistent vomiting or gagging is not normal and may indicate an infection or pyometra, especially if accompanied by lethargy (

Diarrhea: Loose stools or diarrhea after a heat cycle could signify an illness like pyometra. Fetch Pet recommends monitoring dogs closely for diarrhea post-heat (

Loss of Appetite: A decreased appetite or refusal to eat may indicate sickness. According to the VCA, loss of appetite is one of the most common signs of pyometra in dogs (

Increased Thirst: Excessive thirst or urination can point to infections or hormonal changes after a heat cycle. According to Fetch Pet, increased thirst is a potential sign of pyometra (

Discharge: Any abnormal vaginal discharge after a heat cycle, especially if it’s pus-like, bloody, or foul-smelling, requires veterinary attention as it may indicate pyometra or other infections (

Treating Illness

Veterinarians have several options for treating illnesses that may arise after a dog’s heat cycle.

One of the most serious conditions is pyometra, a life-threatening uterine infection. Pyometra often requires surgery to remove the infected uterus and ovaries, called an ovariohysterectomy or spay. Surgery is the most effective treatment to fully remove the infection and prevent it from recurring.

For open pyometra where pus drains from the uterus, vets may try medical management with antibiotics, anti-inflammatory drugs, and intravenous fluids before resorting to surgery. However, medical management has a lower success rate than ovariohysterectomy for complete recovery.

Vets may prescribe antibiotics like amoxicillin-clavulanic acid along with anti-inflammatories like meloxicam to treat pyometra. Hospitalization for intravenous fluids and close monitoring helps manage shock and prevent complications.

Regardless of the initial treatment approach, dogs who have had pyometra are at risk of recurrence or other uterine issues in the future, so spay surgery may still be recommended after medical treatment.


The recovery process after a heat cycle illness will depend on the severity of the condition. For mild cases, most dogs should recover fully within a few days with rest, medication, and supportive care at home. More severe cases like heat stroke can take 1-2 weeks for dogs to recover, and may require longer hospitalization and monitoring [1].

During recovery, it’s important to allow dogs ample rest and limit exercise while their body heals. Provide easy access to fresh water, appetizing food, and comfortable bedding. Monitor the dog for any concerning symptoms like lethargy, vomiting, or diarrhea and notify your veterinarian. Medications may be prescribed to help manage pain, nausea, infection risk, or other issues.

Dogs recovering from heat stroke specifically will need diligent monitoring as complications like organ damage, coagulation disorders, and cerebral edema can arise. Intravenous fluids, cooling, bloodwork, and supportive care are often necessary initially. With proper treatment and time to heal, many dogs can make a full recovery from heat stroke [2].

While the recovery period can be difficult, be patient and keep your dog comfortable. Follow all veterinary recommendations to aid the healing process. With lots of rest and TLC, most dogs overcome illness following their heat cycle and return to their normal happy selves.


In summary, female dogs do undergo changes physically, behaviorally, and hormonally during and after their heat cycles that can temporarily compromise their immune system. While illness is not extremely common, dogs are more prone to certain conditions like pyometra during this time. Staying alert to any concerning symptoms and maintaining good preventive care practices can help keep your dog happy and healthy. Though challenging, this natural cycle is not in itself a cause for major concern as long as proper precautions are taken. To revisit the original question, dogs can occasionally get sick after their heat cycle, but it is relatively uncommon with proper care.

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