09/10/2025
ALLERGIES IN CATS AND DOGS
I have done my best to research the most current data we have regarding allergies in domestic cats and dogs but I am not a dermatologist or a specialist, so I apologize for any errors. I have used only information gathered from peer reviewed and scientifically validated studies, as well as discussions with veterinary dermatologists. I will not include any information on holistic or other data which cannot be verified. If you have been successfully managing your pets' allergies with other means not mentioned, this is in no way intended to disparage what is working for you nor an attempt to change what you are doing. I hope only to inform and educate pet owners. If what you are doing is working, keep doing it!
Let us begin by understanding what an allergy is and why they happen. An allergy is an overreaction of the immune system to a normally harmless substance, known as an allergen. Allergens can be almost ANYTHING—something in the food, in the environment, and from other animals. The symptoms of allergies show differently in humans versus pets; while humans often experience respiratory symptoms like sneezing and runny noses, pets usually show skin reactions such as excessive itching, hair loss and scabs, and chronic ear infections, although respiratory and gastrointestinal issues can also occur in animals. Both humans and pets can suffer from environmental (e.g., pollen) and food allergies, but pets are more prone to contact allergies from items like flea bites, certain fabrics, and shampoos.
If you know anyone with allergies, you know this is something that is rarely cured but typically managed. Symptoms are controlled either through the use of over-the-counter medications such as Benadryl or other antihistamines or with stronger prescription medications or even in-halers. This is because human allergies involve HISTAMINES being released from cells in the body which bind to other cell receptors and this causes the reactions we identify with allergies (runny stuffy nose, red watery eyes, etc). Allergens in humans tend to enter the body through the respiratory system which is why the symptoms tend to be respiratory. With food allergies, the symptoms tend to be GI related. In our pets, the allergens tend to enter the body through the skin thus we get skin issues. If caught quickly, in some mild cases, we are able to manage signs of allergies by bolstering the health of the skin. Skin health is on the microscopic level and not something you would notice by looking. Many dogs and cats have glorious coats and still suffer from allergies. The bad news, as many owners are all too aware, is that antihistamines which work so well for many humans, have no effect on their pet other than the side effect of causing drowsiness. Recent studies show that as little as 20-25% of dogs and cats benefit from human over-the-counter antihistamines. Which does not mean they cannot be tried as they are easy and affordable to obtain so always ask your veterinarian for the proper dose if you wish to try this option.
In the old days, often the only option we had for allergies in our pets was steroids. These work great but they can cause some annoying side effects (drinking more, urinating more, panting, increased appetite, muscles weakness) to dangerous and even deadly side effects long-term (diabetes, liver changes, kidney damage, and even heart damage). Because of this, steroids are avoided as much as possible and, if absolutely necessary to use, do require more frequent exams and blood tests to monitor for any issues before they become irreversible or deadly to your pet. These sever negative side effects are most likely with LONG-TERM use of steroids, meaning months and years of continuous use. However, we did recently have a case where a dog developed a severe dangerous SKIN REACTION to the use of prednisone. While we were able to diagnose and treat to resolve this issue, it was not an inexpensive adventure.
In our modern era, we actually have dog specific medications to help control and manage the symptoms of allergies. We have an oral tablet called APOQUEL and an injection called CYTOPOINT. These are NOT steroids and have been proven quite effective and safe for almost all dogs. In medicine, of course, there are no absolutes, and not every dog can tolerate these nor have the same positive response in control. The bad news is, we won’t know until we try. Apoquel has the benefit of being a tablet you give at home, cytopoint in an injection given at the office as often as every 4 weeks with some dogs going as long as 6-8 weeks before owners note the symptoms returning.
What about cats? Well, the bad news is that neither of these products is labeled for cats and, in the few off-label attempts to use apoquel I have attempted, either there was no benefit, or the cat did not tolerate it (vomiting and GI upset). Cytopoint is a 90% dog monoclonal antibody with 10% mouse; it will cause rapid development of neutralizing antibodies in cats and so will not work/could potentially cause an allergic reaction in cats. It should never be used in cats. Cats do seem to tolerate steroids better than dogs and also, in my experience, do not seem to require them as often as dogs to control allergies. However, the risk of diabetes and heart disease as a side effect does seem more common in cats than dogs so we still try to avoid them. When cats require long term management, we have a medication called CYCLOSPORIN which regulates the immune system and stops the allergic reaction. Typically, cats on this for life will require annual blood tests.
Diagnosing an allergic pet is made based on physical exam findings, the experience of the veterinarian, and by ruling out other possible causes of the symptoms we are seeing. Skin scrapes and cytology, flea control, and even blood tests may be recommended. In some cases, with mild signs, a trial of medication may be deemed appropriate. At the beginning, allergy animals may need frequent rechecks by the veterinarian to ensure a proper response and recovery.
Can we determine what the allergy is? This is often a difficult and expensive question. The gold standard for allergy testing in dogs and cats is dermal testing just like in humans. This is performed by a veterinary dermatologist. The skin test is when small amounts of allergens are injected under the skin, and the areas are monitored for a reaction. There are blood tests available through your veterinarian and many people report positive results from these, but they are not recommended tests by dermatologists. SALIVA AND HAIR TESTING ARE SCAMS AND SHOULD BE AVOIDED!! There are ZERO studies that even HINT such testing is accurate, every study has shown them to be completely inaccurate and a waste of time and money.
Once you get the results, if the issue is food, then you need to avoid these. If it is environmental and the blood test was performed through a reputable veterinary laboratory, desensitization injections are available. These are injections you are able to give at home where small amounts of the allergens are injected into the pet. By slowly increasing the amount of allergens injected over a period of months/years, we are attempting to make the body stop seeing these substances as foreign and thus the immune system will stop reacting. These injections can take several years to have an impact and almost never work as a solo treatment; meaning we still usually need to employ other treatments such as apoquel, diet changes, flea control, etc
