Anaphylaxis in Cats – Causes, Symptoms & Treatment

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What is anaphylaxis?   Symptoms   Diagnosis   Emergency procedures   Treatment

Anaphylaxis in cats

What is anaphylaxis?

Also known as allergic shock, anaphylaxis is a severe, rapid onset and life-threatening reaction to an allergen. Common allergens can include:

  • Insect bite or sting, such as a bee or mosquito
  • Drugs, particularly antibiotics
  • Vaccinations
  • Food allergies

It occurs when the body mounts an over the top reaction to a perceived threat (the allergen), the body will have had exposure to the allergen before, which would have stimulated an immune response, future exposures can result in more severe responses.

During anaphylaxis, IgE (antibodies) bind to the antigen (the allergy-producing substance), which triggers receptors on mast cells and basophils to release their cytotoxic granules. These contain compounds including histamine and serotonin, which result in constriction of the airways. This makes breathing difficult, and causes the blood pressure to drop.


Onset is rapid, usually, within minutes (but sometimes hours) of exposure, common symptoms include:

  • Difficulty breathing, which may include panting or wheezing
  • Rapid swelling of the affected area.
  • Itchiness.
  • Facial swelling.
  • Hives.
  • Pale gums.
  • Gastrointestinal symptoms such as vomiting or diarrhea.
  • Wheezing.
  • Trembling.
  • Low body temperature.
  • Collapse.


Obviously presenting symptoms can be indicative of anaphylaxis. Immediate treatment is necessary to save your cat’s life. However, once the emergency has been addressed,  your veterinarian may wish to run some tests to determine the cause of the allergic reaction (if it is not known). This usually involves a patch test where a minute amount of several common allergens are pricked onto your cat’s skin, the area is then covered and re-examined for signs of redness and swelling 24-48 hours later.

Emergency procedures:

If your cat’s heart has stopped beating, you will need to perform CPR on him. To check for a heartbeat, press against the rib cage over the heart.

checking a cat

If possible, have somebody administer the CPR as you transport your cat to the veterinarian, call on the way so that they can be on standby.

If the cat is wearing a collar, remove it and give plenty of reassurance as he is transported to the vet. Wrap the cat in a blanket and lie him on his side, with the legs slightly elevated.


Anaphylaxis is a medical emergency, and needs immediate veterinary attention. Administration of epinephrine (adrenaline) will be necessary. This is an intramuscular injection which counteracts the adverse effects such as relaxing the airways, making breathing easier, increases blood pressure by causing constriction (tightening) of the blood vessels (which dilate during anaphylaxis) as well as preventing the further release of cytotoxic granules.

Supportive care such as oxygen therapy to assist with breathing as well as intravenous fluids.

How is it managed?

Avoidance of the allergen if possible, this is why it is important to undergo skin patch tests to try and determine the cause.

Switch to a different food or medication if necessary.

If your cat has had an allergic reaction to a drug or vaccination, alert the veterinarian, even if it occurred at his surgery, it is always a good idea to remind him prior to administration of medications.