What are pet allergies?

What are pet allergies?

As with humans and other species, a domestic pet can develop an allergy to a particular substance at any stage of its life. An allergy is defined as the body mounting an immune response to a substance that it’s become hypersensitive to; this includes anything that the pet was previously not triggered by. In other words, the body decides a substance is foreign and responds by attacking it. The clinical signs associated with allergies are effects of this attack, for example:

  • Respiratory signs – sneezing, coughing, watery eyes, wheezing, swollen airway
  • Dermatological signs (skin or ears; often called atopy) – rash, raw/dry skin, lesions, ear discharge, increased scratching or grooming due to itchiness/irritation/inflammation, skin swellings
  • Gastro-intestinal – vomiting, diarrhoea

In dogs and cats, the most common allergy is flea allergy dermatitis (FAD), caused by a hypersensitivity to flea saliva when the pet is bitten by a flea. This can lead to self-mutilation and worsening of the condition which becomes a vicious cycle. Treatment involves resolving the skin damage and implementing an effective year-round parasite control regime.

The next most common sources of allergy are environmental. These include household cleaners, pollens, grass/plants and dust, however there are many other potential environmental causes. The best way to deal with environmental allergies is to minimise exposure to the most common allergens such as pollen and dust. Regular cleaning of the house, washing pet bedding and addressing seasonal allergies are all important.

Another cause of cat and dog allergies is food, however this is actually much less common than most people believe. For example, of all diagnosed allergies in cats, food allergies make up less than 5% of cases, and this number is similar in dogs. Food allergies are different from food intolerance. While a dietary intolerance can cause similar signs to an allergy, affecting the digestion and absorption of food, the difference is that an intolerance does not involve an immune response the way an allergy does.

A food allergy is a reaction to a particular protein source such as chicken, beef, fish, or a non-meat protein, which your pet might previously have been eating for years with no problem at all. Food allergies can cause not just gastro-intestinal signs but also skin signs. The only way to diagnose a food allergy is for your vet to perform a feeding trial over a period of a few months. This involves your pet only eating food that doesn’t contain the most common sources of allergy (chicken, beef and fish); instead, they eat a “novel protein” diet such as venison, egg or lamb that they’ve not previously been exposed to, to determine whether their signs improve. Another option for a dog or cat with a diagnosed food allergy is to eat a prescription diet where the protein has been altered to prevent it from triggering an allergic reaction.

Another cause of allergies, which occurs infrequently, is when a pet has an anaphylactic reaction to a vaccination. This can cause reactions such as swelling of the face or ears, or difficulty breathing. Pets with a history of vaccine reactions can often still be safely vaccinated in the future, with precautions taken such as giving medications beforehand to reduce the likelihood of a reaction. If this occurs with your pet, your veterinarian will determine the best course of action depending on your pet’s individual circumstances. 

While it can be frustrating and time-consuming to correctly identify and prevent further allergic reactions in our pets, there are several treatment and management options available and an allergy does not necessarily mean your pet cannot enjoy a normal lifespan and quality of life. In addition to the strategies mentioned above, in some cases vets prescribe medications such as corticosteroids, cyclosporine, antihistamines or individualised allergy vaccines. Every case is different, and the benefits and side-effects of all medications vary between each patient and pet owner. Therefore, it’s crucial that if you suspect your pet is suffering from an allergy, you seek advice from your veterinarian so they can conduct a thorough investigation and assessment of your pet and then discuss with you the treatment options.


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