Anaphylaxis in dogs is an immediate, severe, life-threatening allergic reaction. Potentially fatal symptoms can appear as quickly as within 5 minutes of exposure to an allergen. The most common causes are insect stings, vaccines, medications, and, rarely, foods.
Typical canine allergic reactions are itchy skin or gastrointestinal signs that develop over time. With anaphylaxis, things happen quickly. Anaphylactic shock is a full-blown, immediate reaction to an allergen.
What Is Anaphylaxis?
Anaphylaxis is a “type 1 hypersensitivity reaction,” which is an immediate, huge reaction to an allergen. It’s an overreaction, basically, with a massive output of histamine by mast cells.
In people, the first reaction is usually respiratory. In dogs, diarrhea and vomiting are the most reported first signs, as the liver is a primary target organ. Swelling (hives), drooling, shock, seizures, difficulty breathing, and death may follow quickly.
Dogs Anaphylaxis Timeline
Signs of anaphylaxis tend to start within 5 to 30 minutes of exposure to the offending antigen and worsen. In dogs, drooling, vomiting, and diarrhea are usually noticed first. If an insect bite or sting is involved, you may see hives or obvious tissue swelling right away. When anaphylaxis hits, it can quickly become anaphylactic shock.
In anaphylactic shock, the dog’s blood vessels dilate, so less oxygenated blood is available to the tissues. The heart speeds up to compensate, but vital organs like the brain and the heart itself are deprived. Anaphylactic shock is not common, but it can be fatal without rapid treatment. If you suspect this severe allergic reaction, head to the nearest veterinary clinic ASAP. Call them on the way, so they know you’re arriving.
Treatment for Dogs with Anaphylactic Shock
Treatment aims at counteracting the histamine release that is behind the clinical signs. Your veterinarian will administer corticosteroids and antihistamines along with epinephrine to work to constrict those dilated blood vessels. Dogs who are severely affected may need an endotracheal tube placed to ensure breathing is not threatened. Intravenous fluids may be required to restore vascular homeostasis (blood vessel function).
People known to suffer from anaphylaxis are often dispensed an EpiPen so they can get epinephrine right away. There are currently no EpiPens for dogs. However, because epinephrine is the main drug for treatment, your veterinarian may prescribe an EpiPen “off label” with very clear instructions for use, if a dog is at risk for anaphylactic shock. This may not be possible with small- or medium-sized dogs.
Prevention of Anaphylaxis
Obviously, if your dog has suffered an anaphylactic event, you want to avoid a recurrence. If the reaction was due to an insect sting, you will need to be super vigilant about checking your yard and home for insects such as bees and wasps.
If you can identify a food trigger, avoid that food. The same for a medication trigger. There are almost always other medications that can provide the same, or very similar treatment.
With vaccinations, if the reaction was mild (simple swelling of the muzzle for example), your veterinarian may break your dog’s vaccines down and limit him to only the necessary core vaccines, given a month apart.
Veterinarians often will pre-medicate the dog by having you come in early for an appointment and giving your dog some corticosteroids, for example. They will often then have you wait for at least 30 minutes before leaving the clinic to catch any possible reaction early on. For some dogs, going to titers to verify immunity is a solution, although many states will not accept titers for proof of rabies vaccination.
