Anaphylaxis in Cats

Barri J. Morrison, DVM
By Barri J. Morrison, DVM on Aug. 17, 2022
White cat on a medical exam at veterinarian office

In This Article


What is Anaphylaxis in Cats?

Anaphylaxis (also called allergic shock or anaphylactic shock) is an extreme allergic reaction that can quickly become a life-threatening event for cats. This is a medical emergency that can be fatal if not promptly treated.

Allergies occur when the body mistakes a substance (called an allergen) for a threat and releases cells to fight off the perceived invader. This allergic reaction is usually minor, such as itchy skin or sneezing. But in serious cases, the entire body can react in anaphylactic shock.

The reaction may occur with the first exposure to an allergen, but more often it is subsequent encounters that lead to shock.

A cat’s lungs are the most common area impacted by anaphylactic shock, which can affect breathing. Other major body systems affected by shock include the gastrointestinal systems (esophagus, stomach, liver, pancreas, and intestinal tract). Fortunately, this condition is rare in cats.

If you suspect your cat is having an anaphylactic reaction, take them to a veterinarian or animal hospital immediately.

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Symptoms of Anaphylaxis in Cats

The most common signs of anaphylaxis occur within seconds to minutes (acute onset):

  • Severe respiratory distress, difficulty breathing

  • Diarrhea

  • Vomiting

  • Excessive drooling

  • Excitement, restlessness

  • Incoordination

  • Pale gums

  • Cold limbs

  • Facial swelling

  • Itchy skin around head and face

  • Seizures

  • Coma

Anaphylaxis can be fatal in rare cases. Although the respiratory and gastrointestinal systems are the organs most impacted, anaphylaxis can affect other body systems as well:

  • Respiratory system (lungs)—Difficulty breathing, open-mouth breathing (panting), coughing

  • Gastrointestinal system (stomach, intestines, pancreas, etc.)—Vomiting, diarrhea, lack of appetite, drooling

  • Cutaneous system (skin)­—Itchy skin anywhere on the body but more prominent around area of allergen contact, facial swelling

  • Cardiovascular system (heart and blood vessels)­—Pale gums, cold limbs

  • Nervous system (brain and spinal cord)—Seizures, incoordination, excitement, restlessness, coma

  • Ocular system (eyes)—Cloudiness or redness in the eyes

Causes of Anaphylaxis in Cats

It’s not possible to predict when anaphylaxis will occur, but cats with known allergies may be at higher risk. This rare but potentially deadly form of shock can occur as an immediate reaction to many things in the environment or from an ingested substance.

Specific causes of anaphylaxis in cats include:

  • Venom injected from insects such as bees, wasps, hornets and fire ants.

  • Reptile venom

  • Food

  • Chemotherapy agents

  • Blood transfusions

  • Antibiotic eye ointments containing polymyxin B (this reaction typically occurs within 10 minutes)

  • Surgery to remove heartworms (heartworm ruptures)

  • Medications taken by mouth, such as antibiotics, steroids, non-steroidal anti-inflammatories (NSAIDs), and opiates.

  • Contrast material used for special imaging such as an MRI

  • Vaccines/antibiotics

  • Physical factors such as cold or exercise

How Veterinarians Diagnose Anaphylaxis in Cats

Diagnosing anaphylaxis can be difficult because of its widespread impact on the body. A veterinarian will suspect shock based on the sudden onset of characteristic signs following exposure to a known or possible allergen.

Uncovering the allergen’s source requires a thorough review of a cat’s medical history, medications, lifestyle, environment, and vaccination history. Any changes to diet should also be reported, including treats and table/human food they ate in the last 24 hours.

Your veterinarian will do a complete physical examination to check your cat’s vital functions and run blood work to look for things like excess inflammatory cells (such as mast and white blood cells) and liver enzyme elevations.

An ultrasound of the abdomen and x-rays of the chest may be recommended to evaluate the heart, lungs, and other internal organs such as the liver and gallbladder for signs of anaphylaxis. Your veterinarian will likely recommend overnight hospitalization.

Treatment for Anaphylaxis in Cats

Anaphylaxis is a life-threatening emergency that requires immediate medical intervention. While the diagnosis may not be made immediately, your vet will work quickly to treat your cat’s symptoms.   

The goal of treatment is to stabilize the cat, ensure the airway is clear, and insert an IV catheter to administer fluids, medication, and other therapies. An injection of epinephrine (the hormone adrenaline) will be given to counteract the effects of the immune system reaction.

Epinephrine will help stimulate the heart, open the tubes in the airway, and remove the inflammatory cells from the blood stream, which will reduce the symptoms of anaphylaxis. In severe cases, a breathing tube may be inserted to provide oxygen.

Other medications such as steroids and antihistamines can also be helpful in the long term and play an important role in preventing a late-phase reaction, a recurrence of clinical symptoms.

Recovery and Management of Anaphylaxis in Cats

Cats experiencing anaphylaxis should be monitored closely by a veterinarian for at least 48-72 hours after the reaction, even if the clinical signs appear to improve, because rebound reactions can occur.

The prognosis for an anaphylaxis depends on its severity and how fast symptoms progressed. Your vet can help develop strategies to avoid the trigger if it is identified. Allergens can in some cases be uncovered through skin allergen testing.

Anaphylaxis in Cats FAQs

How long does anaphylactic shock last in cats?

Anaphylactic shock can last from just a few minutes to periods up to 72 hours. Cats that experience anaphylaxis should be monitored closely by a veterinarian for at least 48-72 hours after the reaction. It’s important they are observed for an extended period, because clinical signs can improve and then quickly reappear after several hours.

How long does it take a cat to recover from an allergic reaction?

Once the allergen is removed, it can still take a few days for all symptoms to resolve. Animals often require close monitoring in a vet hospital for 24-48 hours after treatment has begun, and up to 72 hours after the signs began.

Featured Image:

Barri J. Morrison, DVM


Barri J. Morrison, DVM


Barri Morrison was born and raised and currently resides in Ft. Lauderdale, Florida. She went to University of Florida for her...

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