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  • Writer's pictureStittsville Kanata Veterinary Hospital


Basics Anaphylaxis is a severe and potentially life-threatening allergic reaction that

can occur in both dogs and cats. It is a rapid and intense immune response

to an allergen, which is a substance that triggers an allergic reaction.

Anaphylaxis can lead to serious respiratory, cardiovascular, and

gastrointestinal complications.

Urticaria: cutaneous manifestation of anaphylaxis, consisting of pruritic


Angioedema: nonpainful cutaneous and visceral edema (regional or

generalized) that is one of the hallmarks of anaphylaxis

Anaphylaxis does not always involve a previous and sensitization.

It should be suspected in patients with unexplained acute cardiovascular and

respiratory collapse. Fluid therapy and epinephrine are the first lines of

treatment for severe anaphylaxis.

Types Type I Anaphylaxis: This is the most common type and occurs within minutes

of exposure to an allergen. It involves the release of histamines and other

chemicals, causing rapid and severe symptoms.

Type II Anaphylaxis: This is a more delayed reaction that can occur hours

after exposure to an allergen. It is less common and involves a different

immune response.

Causes Anaphylaxis can be triggered by various allergens, including insect bites or

stings, certain foods, medications, vaccines, and environmental substances

like pollen or dust.

Signalment Pets of any age, breed, or sex can develop anaphylaxis. However, some pets

may be more predisposed due to a history of allergies or sensitivities.

Concurrent Conditions Underlying allergies, asthma, or other immune-related conditions may

increase the risk of anaphylaxis.

Pathophysiology Anaphylaxis occurs when the immune system overreacts to an allergen,

releasing an excessive amount of histamines and other inflammatory

substances. This leads to widespread blood vessel dilation, decreased blood

pressure, and compromised organ function.

Clinical Signs - Early Stages vs Later Stages

Early Stages: Itching, hives, facial swelling, vomiting, diarrhea, restlessness,

difficulty breathing, coughing, sneezing.

Later Stages: Weakness, collapse, pale gums, rapid heart rate, low blood

pressure, loss of consciousness.

Diagnosis Testing Diagnosis is based on clinical signs, history of exposure to allergens, and

ruling out other potential causes. It can be challenging as symptoms can

mimic other conditions.

Blood pressure: monitor for hypotension

CBC, serum chemistry, urinalysis: generally unremarkable, may have

decreased platelet count

Thoracic radiographs: to rule out pulmonary disease if respiratory distress or

tachypnea is present

Heartworm testing: antigen (dogs) or antigen and antibody (cats)

Coagulation testing may reveal hypocoagulability

General blood work including Slide Agglutination Test to check if there is

increased immune system activity damaging RBCs which could be fatal if not

recognized in time.

Challenges in Diagnosis Identifying the exact cause can be challenging due to the diverse potential

underlying allergens.

Treatment The main goal of treatment is to stabilize the pet and reverse the allergic

reaction, as well as to manage complications and prevent recurrence. Fluid

support may be needed.

Medications & Handling Epinephrine: Counteracts severe symptoms, but should only be administered

by a veterinarian.

Antihistamines (Diphenhydramine, Famotidine) and Corticosteroids: Help

control inflammation and allergic reactions.

Fluid Therapy: Supports blood pressure and organ function.

Bronchodilators: Open airways in cases of respiratory distress.

Special Medicine Handling

Administer medications as directed by your veterinarian. Epinephrine should

be handled with care due to its potency.

Common Complications Common: Skin infections from scratching, prolonged respiratory distress.

Rare: Blood clotting issues, kidney or liver damage.

Rare & Severe Complications

Worst: Severe respiratory or cardiovascular collapse, leading to death.

Effect on Lifespan and quality of life

Untreated anaphylaxis can be fatal. Prompt treatment can improve the

chances of recovery, but long-term consequences can affect the pet's quality

of life.

Prognosis - Early Stages vs. Later Stages

Early treatment greatly improves the prognosis. Late-stage anaphylaxis has a

poorer prognosis due to the increased risk of severe complications.

Signs of Recovery Improved breathing, stable heart rate, regained consciousness, decreased swelling.

Recovery Testing Blood tests, imaging, and monitoring vital signs can help confirm recovery.

Likelihood of Recurrence

Pets that have experienced anaphylaxis are at higher risk for future episodes.

Signs to Watch Out For Persistent coughing, difficulty breathing, swelling, restlessness, lethargy.

In case of deterioration of pets condition or delay in recovery

Contact your veterinarian immediately. Additional treatments, monitoring, or

hospitalization may be necessary.

Recommended Monitoring

For mild cases (skin reaction only), monitoring at home for recurrence

For severe cases: Frequent monitoring should be continued for 24-48 hours

after reaction.

• Heart rate, respiratory rate, respiratory effort, pulse rate, pulse quality,

mentation, mucous membrane colour, capillary refill time, temperature,

urine output

• Blood pressure

• Electrocardiogram

• Pulse oximetry or arterial blood gases

• Packed cell volume and total solids

• Serum biochemistry analysis

• Coagulation testing

Prevention Identify and avoid triggers, discuss allergen-specific immunotherapy with

your vet.

Feeding Instructions Allergies to certain foods can trigger anaphylaxis. Consult your vet for

suitable diets if food allergies are suspected.

Zoonoses Anaphylaxis is not contagious, but some allergens can affect humans.

Discuss potential risks with your veterinarian.

This is a generalized information handout. Always consult your veterinarian for personalized advice and care for your pet. SKVH Client Handouts © 2023

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