Allergies: Causes, Diagnosis and Treatments

This is a big topic, so today I will do my best to pare it down into palatable sized bites with the basics of allergies and what options we have for diagnosing and treating them.  More research or an appointment with your veterinarian may be necessary to discuss all avenues of diagnosing and treating suspected or known allergies in your pet.

Environmental Allergies

There are many things in a dogs’ or cats’ environment that can create a hypersensitivity.  Many of these allergies have a seasonal effect, much like we see with our own human allergies.  Pollens, grasses, trees, spores, insects or other materials can cause allergies often in this seasonal pattern.  Some other environmental allergens can be year-round, thus making them difficult to differentiate from a food allergy.  These might include dust mites, fleas, yeast, moulds, etc. that are in a home year-round.

Food Allergies/Adverse Food Reactions

Any component of a diet can be the cause of an allergy, but more often than not the suspected ingredient is the protein source, followed by the carbohydrate source.  Often a patient is allergic to more than one food source, thus making the hunt for the right diet more complex.  Generally, as the diet is fed every day the pet is often going to experience fairly severe allergy symptoms year-round, with no periods of relief.  Common allergens include chicken, beef, rice, corn, but any ingredient has the ability to cause an adverse food reaction.

Clinical Signs of Allergies

·      Itching/scratching

·      Licking paws

·      Chewing or “corn cobbing” legs

·      Ear infections

·      Bum irritation/licking/scooting, anal gland impactions

·      Chronic GI upset (vomiting, diarrhea, loose stools)

·      Hair loss

·      Redness or skin irritation

·      Hives

·      Facial swelling

·      Thickening and darkening of the skin due to chronicity of skin irritation

·      Secondary bacterial infections

·      Secondary yeast infections

·      And more…

Diagnosis of Allergies

Patterns and severity of clinical signs can sometimes help us better determine the likely cause of pet allergies.  Food allergies may be more likely to show up as irritation of the paws, ears and bum.  They may also be more severe as the allergen is being fed daily.  Environmental allergies are commonly seen on the ventral or underside of the dog or cat, where their bodies make contact with things like grass and other surfaces.  Bellies, chest, neck, face, armpits and elbows are common spots in this case.  Symptoms may be less severe with environmental allergies than seen with a food cause.  Flea allergies often show up over the tail head and lower back of the dog, and cats we often see a lot more itching and irritation around their neck and head.

An acute hypersensitivity reaction to a bug bite, sting or medication is more likely to show up as hives, facial swelling, vomiting, diarrhea and lethargy.  Seeking medical attention is a good idea, and urgent if there is difficulty breathing or your pet’s colour is no longer nice and pink (gums and tongue).

Other than distribution and severity, we are able to test for many environmental and insect allergens through a blood draw or intradermal skin testing.  This allows for identification of specific allergens, which can than be turned into allergy shots or sublingual immunotherapy to help the body become desensitized to these antigens.

For suspected diet allergies, a diet trial is the best way to diagnose it.  Completely switching to a hypoallergenic diet and strictly feeding 100% that food with no treats, human food, or flavoured supplements/medications can often tell us if your dog or cat has a food sensitivity.  Though difficult to maintain this strict diet for 8-12 weeks, we can often see amazing improvement to our pet’s health and well-being if we are no longer feeding the allergen to them on a regular basis and this is the sole cause of their clinical signs.

Often allergies are presumed to be a cause of clinical signs based on ruling other medical concerns out and through the response to therapy.  Not all itching and licking is an allergy, and it is worth having a conversation with your veterinarian to determine the cause of your pet’s clinical signs.

Allergy Treatment

With time the veterinary world has expanded treatment options for patients with allergies, which is great news as not every patient finds relief with every therapy.

Traditionally corticosteroids were our main treatment option, and they are still used today though they tend to have more side effects than other therapies on the market.  They work by inhibiting pathways of inflammation and pain, thus reducing your dog or cat’s need to itch and feel so uncomfortable.  Oral, injectable and topical products are available.

Newer options are now on the market such as JAK inhibitors.  These medications (Apoquel and Zenrelia so far) stop the itch pathway by inhibiting an enzyme called janus kinase and reduce IL-31 stimulation (interleukin-31 a signaling molecule).  These can be quite effective drugs for allergy patients, and have fewer side effects than traditional steroids.

Cytopoint is a monthly injectable therapy that goes under the skin, much like a vaccine, and works as it is an antibody to IL-31 for dogs only.  As this is an antibody injected into the patient, it works by blocking the IL-31 signal pathway by neutralizing the IL-31 cytokine before it can even bind to its receptor, thus blocking any downstream itch and inflammation signalling.

Allergen-specific immunotherapy is created for your pet based on allergy testing.  It is very safe and a great long-term treatment option for our patients.  Specific treatments in injectable or under-the-tongue formulations are made for your pet and are micro-doses of the allergens in order to help create tolerance to these antigens with the potential to cure the patient of those specific allergies.

Cyclosporin is a great therapy option for environmental allergies/atopy.  It works by inhibiting T-cell function which is our cell-mediated immunity.  Cats often see good benefits from this treatment, and some dogs do as well.

Antihistamines may be helpful when given pre-emptively, but will not help once there is already inflammation and discomfort.  It can also be used in conjunction to reduce the dose of steroids.  Caution is warranted when using these medications that the only ingredient is the antihistamine, and not in combination with decongestants, acetaminophen or other drugs as many of these can be harmful or toxic to your pet.

Finding a diet that works for your pet can be key, and taking the time to find the right one can be well worth it as that might be the “cure” your dog or cat needs to be done with allergies!

And don’t forget about topical treatments, such as shampoos, conditioners and mousses that can really help a patient to reduce skin inflammation, skin infections, remove allergens directly from your pet’s coat and skin, increase moisture and re-establish the protective skin barrier.

Allergies can be a frustrating diagnosis to work with, both for your pets and yourself.  If one therapy does not appear to be helping, it is worth trying others, as each individual pet may need their own individualized treatment plan.  Your veterinarian is a great resource, and having frank conversations about allergies and how best to help your dog or cat can be worth it in the long-term.  Patient comfort and happiness is important to me as a vet, as is working closely with my clients to find a treatment plan that they can be managed at home and provide the relief they are looking for.

Wishing you all a wonderful Summer!

Dr. Hillary