In this second episode Dogtor S, delves into one of the most commonly encountered conditions in our furry friends, allergies. Presenting primarily around dogs, this podcast and blog post focuses on the clinical signs and various treatment options for allergies.
Hello to all and welcome to the second of a 5 part podcast
introduction series for paws press play, a podcast where I, Dogtor S, hope to
shine some light into the veterinary profession and the various diseases that
our beloved pets may suffer from. I hope you enjoyed the introduction podcast
and stay tuned for more. So sit back, paws and press play.
Imagine this scenario: you’ve just come home from work and
realize that your beloved dog, Rex is not waiting at the door to greet you like
usual. “Hm,” you wonder to yourself, “This is quite unlike him, but he’s done
this before a couple of times I guess.” You set your bag at the stairs and
start to call for him, you can hear him coming from the other room. He rounds
the corner and your heart leaps up into your throat. His face is swollen like a
balloon! Rex’s eyes are essentially swollen shut and his muzzle is large and
bright red. His face looks like a cherry tomato or a strawberry! So, you swivel
back the way you came and load Rex into the car to get him into the vet. You
may of course take a picture of him on the way, for proof of course… What’s
happening?
Rex in this instance is having most likely an anaphylactic
type reaction to something. These are severe allergic reactions where the
body’s immune system responds to the point of an excess to some stimulant. We
rarely get to know exactly what that stimulant is but it can be essentially
anything, often time’s plant material or a bug bite. The swelling of Rex’s face
is very commonly seen, but you can also see swelling of the feet, diarrhea,
vomiting, and/or difficulty breathing. When caught early on in the process this
is very treatable and usually just requires a quick trip to the veterinarian;
whereas if left alone things can progress and this type of allergic reaction
can be life threatening. The primary treatment of choice is an injection of
Diphenhydramine or Benadryl (yes just like the one sitting in your medicine
cabinet, however in an injectable form) as well as usually a steroid. These
medications work by blocking the overreaction of the immune system in different
ways. The antihistamine, or Benadryl, blocks histamine release from white blood
cells that are responding to the allergen. Histamine causes itchiness, redness,
and irritation, and excessive histamine can cause low blood pressure, swelling,
hives, and difficult breathing. The
steroid will work by a slightly different mechanism and will suppress
essentially all of the body’s cellular immune response to whatever Rex got into
or stung by. This will prevent the further recruitment of inflammatory cells
like Mast cells which carry histamine. Usually effects of these two injections
are seen almost immediately, and the swelling can resolve within a couple of
hours. Occasionally after these episodes you may begin to see diarrhea or other
stomach upset, this is consistent with the large increase in histamine and the
reaction of dog’s bodies to the stress of this event. You must keep in mind
when seeing this on your animal that, while it is very alarming to see for you,
vets see it all the time. So, it is absolutely something that requires
emergency attention, but your veterinarian will likely handle it in a very calm
and sometimes even light hearted manner. Our pets tend to look fairly cute when
their face swells up.
Now, the reaction that Rex had is a bit more extreme than you’ll typically see. Perhaps a more common scenario would be that you see your dog licking his or her feet, scratching their face, or making repeated trips to the veterinarian for ear infections. These are the most common clinical signs that afflict patients with allergies. These can be environmental, like Rex’s, but they can also be related to the diet that they are being fed. Now this is not to imply that your diet is not high quality, rather research has shown that dogs are most frequently sensitive to the proteins in their food instead of the other ingredients. Fortunately, in today’s day and age we have many options to treat allergies.
Your veterinarian may talk to you about them in varying order, but I typically approach the cases like this. If the patient is middle age, usually between about 2-10 somewhere I will lean more towards environmental causes. The easiest place to start is an antihistamine, similar to what I discussed with Rex; however, given orally and long term. These are effective in only about 30-40% of dogs at controlling their itchiness long term. However, they are cheap and over the counter products that can provide immense relief in some dogs. Patients that are less than 2 or older than 10 become better candidates for a diet trial to assess whether they are allergic to the proteins in their foods. There are two primary means of doing this, Number 1 is called a novel protein diet. This is a diet that exposes the dog to a protein source that they have likely not been exposed to before i.e. Kangaroo or Duck. The alternative is a hydrolyzed protein diet, this is where the proteins in the food are modified so that they do not directly stimulate the immune system and create the clinical signs that you’ve become used to seeing. These are somewhat trickier to pull off as an accurate diet trial typically requires four consecutive weeks and up to 8 weeks of consistent feeding of only this food, they cannot get literally anything else.
As I said before, we are fortunate that nowadays there are several options so the following treatment options are certainly available; however, with these treatments come usually either increased costs, increased side effects, or both. As a side note, this should not imply that Antihistamines have no side effects; however, we rarely see any significant ones beyond sedation. So, now we will run through the list of the remaining options. Apoquel is a tablet that is given twice daily for 2 weeks and then once a day for maintenance therapy. This drug targets receptors called Janus Kinase receptors that are involved in the allergy process and you can see benefits within hours of giving the first dose. The downsides are that this drug is costly, especially for larger dogs. For a dog that is about 20-30 pounds you should likely count on between 100-200/month depending on where you get it. Additionally, being a newer drug, the side effects are not well known at this time. It appears to have very few adverse or negative reactions, but nonetheless we just don’t know the full gamut of what can happen.
Cytopoint, or Lokivetmab, is a monthly injection that is given at your veterinarian. This drug targets an interleukin which is a type of molecule that the body releases in response to inflammation or infection. It targets IL-31 which is specifically involved in the allergy process. The downsides are that it again can be expensive. While this drug, like Apoquel appears safe, its side effects are not well known. Plus sides are that it can be extremely effective and can sometimes be used on an every 8 week basis.
As a side note for Cytopoint and Apoquel, since they both technically affect the immune system they may carry a label, or you may find statements online that they increase the risk for certain cancers. This is predominantly because of their mechanism of action and they are required to warn of this potential risk. I should say that in my experience I have not found development of cancers to be an issue with these drugs.
Corticosteroids are synthetic steroid type drugs that are effective at treating many immune related diseases. The most common ones you’ll likely encounter are Prednisone (orally), Dexamethasone (oral or injectable) or Triamcinolone or Kenalog (Injectable). Steroids are extremely effective management drugs for chronic allergy. They are cheap and very good at what they do. Steroids, unfortunately, are more likely to have some notable side effects, especially at higher doses. This includes increased thirst, hunger, urination, and even some changes in liver enzymes and other organ functions especially with longer term therapy..
Immune therapy is an option that is available in many locations nowadays. This is a technique that is also performed in human medicine whereby the doctor performs an allergy test and then formulates an injection to slowly help the body acclimate to the allergens that it has been overreacting to. This in many areas is only available through a dermatologist. These are veterinarians that have graduated from veterinary school and have gone to get more training specifically in dermatology. This can provide some great relief for some patients as well, but you should expect to spend thousands of dollars rather than hundreds to get entirely through this therapy.
Finally, the last option is a drug called cyclosporine which targets T cells. T cells are a component of the body’s cell mediated immunity. The downsides to cyclosporine are that it is incredibly expensive for animals at this time. Additionally, it can cause GI upset and some changes to the liver enzymes as well. That’s not to say that it is unsafe to use; however, it is not my first choice in many cases. Some dogs receive immense benefit from this drug, so don’t completely discount it.
I’ll wrap this segment up now by saying allergy can be a severe impact on your pet’s quality of life. A dog that is chronically itchy tends to be predisposed to both bacterial and yeast infections of the skin and ears and frequently will require multiple vet visits to get stable. However, once stable, patients can go on to be happy and healthy for their full lifespan. So it is important to consider an allergy if you notice your pup doing these behaviors.
I know I have focused this podcast primarily on dogs; however, cat allergy can be quite different. Cats pose a more difficult problem as they are more likely to have anxiety or psychogenic related causes for itching and so the diagnosis and treatment of allergy can be a lot different in cats. Psychogenic refers to things that originate from a psychological cause, rather than a physical one. Basically not a true itching secondary to an allergy, but rather secondary to the cat’s own mind. Nonetheless, cats can be allergic too, so if you notice clinical signs in your cat this too could be an indication to get into your veterinarian. I will be putting a separate podcast about cat allergies soon.
Finally, dogs can also have psychogenic allergies. These can be very difficult and tedious to diagnose because they are found by essentially ruling out any other source of itching. So, in some cases, the medications that we reviewed above may not end up being the answer. Fortunately veterinary medicine has many options for dogs nowadays with allergies, and so ultimately it is just getting through the process of finding what works. This has been Dogtor S, I hope you enjoyed this episode and I look forward to the next one. Don’t forget to leave feedback, request a topic, or donate if you wish. We will see you in the next episode.
Useful Resources:
https://www.zoetisus.com/products/dogs/cytopoint/ https://www.zoetisus.com/products/dogs/apoquel/index.aspx
https://vcahospitals.com/know-your-pet/allergy-general-in-dogs
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