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How Can Stress Make Your Pet Ill?

In our pets, stress manifests in many forms, such as bladder infections and high blood pressure.

Reducing stress in your pet could mean happier, healthier times ahead. By: digitalcj

Could stress-related illness be making your pet sick?

If your cat or dog suffers from skin problems, vomiting, diarrhea, bladder issues or even seizures, have you considered stress as a contributing cause?

With April being National Stress Awareness month, now is the ideal time to take stock.

Physical Responses to Stress

We share a lot in common with our pets. This includes the “fight or flight” response, which is what leaves you with a pounding heart and dry mouth when faced with that terrifying…spider. This is the trump card in animal survival stakes — that racing pulse sends oxygenated blood flooding to the muscles that are ready to fight or flee.

That same “stress” response provides a buffer or slack in the system, used for coping when extra demands are placed on the body. A bit like pressing the gas pedal in a car, it gives a pet the flexibility to come up with the goods when required. Indeed, a lack of ability to respond to stress causes illness in its own right.

But too much of a good thing means the body is constantly soaked in the stress hormone cortisol, a naturally produced steroid. In limited quantities, it’s beneficial, but too much? That’s when problems start.

Altered Blood Picture

If you think stress is all in the mind, think again. There are shifts in the number of types of white blood cell in the bloodstream that are so characteristic that the pattern is given the name “stress leukogram.”

Typically, this is a rise in neutrophil numbers and a fall in lymphocytes and eosinophils. This is down to the influence of cortisol on the body, but the effects don’t stop there.

Weakened Immune System

Cortisol release changes the balance of the immune system’s defenses. It weakens how the body fights bacteria and viruses, making it more vulnerable to infection. Signs of this are recurrent skin infections or a simple cold that refuses to clear up.

Stress could result in a weakened immune system in your pet. By: Alessandro Valli

Stomach Ulcers

It’s not just people who get stress-related ulcers. That natural steroid production acts on the stomach and

  • Decreases the amount of protective mucus lining the stomach
  • Slows up repair of the stomach lining
  • Increases the production of stomach acid

Add this together, and you get acid eating away at the stomach lining. Symptoms of this include poor appetite, regular vomiting (perhaps with blood) and restlessness linked to eating.

Inflammatory Bowel Disease (IBD)

IBD is a complicated condition with lots of factors at work, but stress also has a part to play.

It’s thought the weakened immune system doesn’t patrol the gut wall as it should and allows food antigens to pass between the cells and promote an inflammatory response. This interferes with how the bowel processes food and results in diarrhea. Just another example of how stress has a very real impact.

Blood Pressure, Blindness and Seizures

It follows that if cortisol pumps up the heart, this also increases blood pressure. Prolonged stress causing long-term raised blood pressure is linked to blindness (especially in cats); kidney, liver and heart damage; and seizures.

When Cortisol Is Necessary

The opposite side of the coin is a dog or cat who cannot mount a response to stress.

This deficiency of production of natural stress hormones such as cortisol also causes significant illness. In dogs, we recognize this as Addison’s disease; in cats, this shows as feline interstitial cystitis (FIC).

Addison’s Disease

This condition is due to the body not being able to respond to stress.

Lack of cortisol production (due to damage to the cells producing it…but that’s another story) means the body can’t produce extra glucose when it’s needed, and the pet’s blood glucose falls dangerously low. There are other effects as well, which results in waxing and waning sickness and diarrhea, eventual collapse and possible death.


It’s thought about 65% of cats who suffer regular episodes of bladder inflammation (feline lower urinary tract disease, or FLUTD) have FIC. In part, this results from the body’s adrenal glands not producing enough cortisol but plenty of adrenaline. This causes a release of neurotransmitter chemicals that directly irritate the bladder lining, creating inflammation that gives the cat the desire to strain in the tray.

Stress has a real and physical connection to illness in our pets. Of course, stress is just 1 of many factors that cause ill health, so always get your sick pet checked out by a vet.

In the meantime, know this: Reducing stress can help keep your pet healthy.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed April 7, 2017.