Anaphylaxis in Dogs

An allergic reaction is caused by the immune system in response to a triggering substance. The body identifies the substance as dangerous and releases histamines and other inflammatory chemicals to counter the perceived infection. Allergic reactions in dogs can vary in strength and symptoms. In rare cases, a very extreme reaction will cause generalized systemic distress throughout the body. This usually occurs in response to a known allergen, one which your dog has experienced before. Very extreme allergic reactions are called an anaphylactic or allergic shock, or sometimes just anaphylaxis. This is a life-threatening condition when left untreated; however most dogs will recover if they receive medication in time.

In dogs, the organ most immediately affected by anaphylactic shock is the liver, so extreme digestive upset is sometimes the first symptom. Unlike humans, there may be little or no swelling of the face or throat. Seek immediate medical attention if your dog exhibits any of the following symptoms, especially if the response is triggered by a potential allergen:

• Itching or redness at the site of contact
• Sudden diarrhea
• Excessive drooling
• Vomiting
• Difficult noisy breathing
• Fast heart rate
• Seizures
• Weak pulse
• Signs of shock
• Coma

Less serious responses are also possible. These symptoms can still be important since allergic shock may develop later or with repeated exposure to the allergen. Common signs your dog may have allergies include:

• Localized skin problems:
• Hives
• Swelling
• Itchy rash or bumps under the skin
• Raised hair follicles over an area of rash or swelling
• Congestion
• Chronic bronchitis with a dry cough
• Difficulty breathing during physical exertion
• Vomiting in response to certain foods

Types

Allergic reactions are a Type I adaptive response. This means the body reacts immediately and directly to the trigger.

There are several general categories for allergic reactions:

• Localized allergic reactions are minor and limited to the specific area which came in contact with the trigger. Most develop less than half an hour after exposure. Common localized responses include itching skin and small areas of swelling. These should be monitored closely and may still require medical attention.
• Systemic allergic reactions affect major systems in the body. They may develop immediately or within a few hours. They are usually in response to an allergen with which the dog has had prior contact, so the body will recognize the substance and react more violently. These reactions are defined as an allergic shock, and they will result in death without immediate medical treatment by a veterinarian.
• Seasonal allergies usually manifest as seasonal congestion or bronchitis.
• Chronic allergies are long-term conditions. It can sometimes be difficult to pinpoint the exact cause.
• Atopy or Allergic skin reactions are common in about 10% of dogs. Some breeds including Dalmatians and Terriers are more susceptible.

Substances which can trigger allergic shock in dogs are fairly similar to those which cause the same condition in humans:

• Food or chemicals used to prepare food
• Penicillin and other medications
• Injections including vaccinations
• Insect bites

Like humans, dogs can develop long term allergies to dust, mold, pollen, or even dander. These allergies won’t usually lead to anaphylactic shock, although they could indicate a predisposition to allergic reactions.

A veterinarian can usually diagnose allergic shock based on the symptoms. Knowing the triggering substance and your dog’s medical history can also help. Treatment will need to happen immediately in order to save your dog’s life, so handle the situation as an emergency and call the nearest veterinary clinic as soon as you notice any symptoms of anaphylaxis in your dog. Drive your dog to the veterinarian as soon as possible. Endeavor to keep your dog comfortable and maintain an open airway.

Seek medical help even for minor localized responses, especially if your dog has experienced a prior allergic reaction. Diagnosing and monitoring all your dog’s allergies will help to prevent life-threatening emergencies.

Sometimes with milder, long-term allergies, such as those to dust or mold, it can be difficult to determine the exact substance causing the problem. Veterinarians will test several possibilities by exposing your dog to a small amount of the substances and watching for reactions. Even if a diagnosis is difficult, it is often possible to treat the symptoms with medication.

If a dog is experiencing anaphylactic shock, the veterinarian will administer emergency doses of adrenaline, usually by injection. Antihistamines and hydrocortisone are commonly given as well. The dog may need an IV to avoid a drop in blood pressure as well as additional oxygen. This can be a scary situation, but treatment is very effective and most dogs who are treated in time will recover with no detrimental effects. Your dog may need to stay in treatment for several days to ensure that all systems have returned to normal.

The veterinarian will usually take steps to avoid another attack. If the cause was a medication a new drug will be prescribed; if the cause is food, the veterinarian might put your dog on a special diet. The vet may also prescribe an Epipen for your dog. An Epipen is a single dose injection of adrenaline which you will be able to administer in the event of another attack. This can will to control anaphylactic symptoms until you are able to get professional help. It’s not a substitute for emergency medical treatment by a veterinarian.

Allergy medication is often prescribed for milder long-term allergies also. If a the trigger is determined for skin allergies, the vet will treat the dog by injecting small amounts of the substance until a tolerance is formed and the allergic reactions cease. If this is ineffective, or the trigger is not determined, the symptoms can still often be treated with antihistamines and other medication.

If dogs are treated promptly, they will generally make a full recovery from allergic shock with no negative consequences. Steps may need to be taken to avoid a reoccurrence of the incident however including diet, medication and lifestyle changes. These should be followed rigorously since any anaphylactic attack can easily be fatal, especially since it’s somewhat harder to get emergency medical treatment for a dog than for a human. New allergies can develop quickly, so it’s a good idea to watch your dog’s reactions very closely anytime he tries a different food or a new medication.