Itching to Learn about Allergies?

The itchy dog or cat; by far the most common issue I’ve seen over the years as a veterinarian, so let’s take a look at the reasons behind the itching and how we can best treat these animals.

First, consider all the reasons why your dog or cat could be itchy:

• Atopy: pollen allergies that are seasonal and makes them itch at their ears, face, groin, armpits, feet or under their tail.
• Food allergy: non-seasonal itch of ears, feet, or under their tail.
• Parasites: mange, a non-seasonal itch anywhere on the body; and fleas, which makes them itchy over the tail head.
• Contact allergy: itchy where the animal comes in contact with something, or hypersensitivities to their own normal skin inhabitants (yeast and bacteria). 

The most important thing I can do is obtain a really good history from the owner about this itchy issue.

Why? Because in order to treat the current problem and anticipate how we are going to prevent further problems, I need to know the following information:

• The current age of the animal. Younger animals are more prone to things such as mange, versus an older animal. Older animals are more prone to inhalant and food allergies.
• Where does the animal itch? Flea allergies, for instance, are much more likely to cause itching above the tail head versus, let’s say, food allergies in cats that cause them to itch between the eyes and ears. Food allergies and inhalant allergies will cause itching in many of the same spots. Inhalant allergies, or “atopy”, are primarily due to pollen. Inhalant allergies cause certain types of cells to become activated and release substances called histamines that lead to itching. These histamine-containing cells are primarily located in the skin of animals; in humans, histamine releasing cells are mainly located in the respiratory tract, nose and eyes.
• Which came first, the itch or the scab? Most of these itchy dogs will present with a concurrent bacterial infection of the skin; knowing which arrived first helps immensely but it requires a very observant owner. An itch can lead to skin infection, but a skin infection can also lead to an itch. Knowing which came first is monumental in that primary bacterial infections (scabs first) are treated with antibiotics alone when caught early, whereas the atopy (itching first) dog needs steroids, antihistamines and fatty acids to treat and prevent their itching. Knowing this difference will help anticipate which preventative measures will be most likely to succeed.
• When did the itching start? Seasonality of the itch is the key to diagnosing an itchy dog or cat. The inhalant allergies from pollen will occur during months when things bloom – easy to realize when you live in the north and have snow that covers the ground for 6 months of the year, but a little more tricky when you don’t have winter. Winter itching only would make me consider household dust mites, molds, etc. as a culprit. If we have an animal with a year-round, non-seasonal itch, then we start to consider the following: food allergies, hypothyroidism, Cushing’s disease, sensitivities to their own skin inhabitants such as yeast or staph bacteria, and parasites.
• How severe is the itch? Severe itching that wakes the owner up at night always makes me consider mange. There are two types of mange: 1) Demodectic mange which dogs under one year of age get, and 2) Sarcoptic mange, which is more common with older dogs and occasionally cats. Demodectic mange will present with a patchy hair loss pattern and little or no itching. Sarcoptic mange will present with a dog that almost never stops itching and has hair loss due to scratching. Both are diagnosed with skin scrapings and can be treated by your veterinarian successfully.
• Itching that doesn’t wake the owner up still is valid, and I still will do a skin scraping to rule out mange. The level of medication to treat the itch will be dictated by what we find to be the cause of the problem if we are confident that we understand it.
• What medications have been tried, and what was the result? This can tell me a ton. For instance, food allergies don’t typically respond well to steroids while atopy cases do. Parasite issues often are not helped at all, and can actually worsen with the use of steroids, and primary cases of staph bacteria hypersensitivity will improve with antibiotic use alone.
• What food changes have been tried? For many years, my only option with suspected food allergies was the food trial. Dogs and cats, if allergic to their food, are actually allergic to the proteins in the food – sometimes many proteins or just one protein. So to do a proper food trial, we change the dog or cat to a food with as few proteins as possible and hopefully new proteins that they have never been fed before. All other food items need to be eliminated and a minimum of two months is needed to judge whether the food change has made a difference. Two months may seem like a long time, but it can take that long for the animal to expel all previous food allergens from their former diet. This sure can be a drag to do correctly, and few clients can make the two months. The good news is there are two other options in lieu of the food trial that can be done: 1) Blood tests that detect certain antibodies that are used to correlate exact proteins that lead to allergies or 2) A skin injection test to find those protein culprits. I personally have had pretty good luck with the food allergy blood tests and use them regularly.
• Has there been any blood work done? Hypothyroidism is a very real problem in certain breeds and can lead to many chronic skin and non-skin issues. Several common symptoms are the itchy dog or a dog that has a thin haircoat. Never discount hypothyroidism with a long-term itch that just doesn’t respond well to treatment or continually recurs. Often on first presentation I may test a dog that is itchy for a long period of time, has hair loss and has a “thin skin” feel to them. Easily treated with thyroid supplementation, it is a straight-forward fix in most instances. Routine blood work would also include liver and kidney function tests, urinalysis and complete blood counts. This could help rule out Cushing’s disease, which in a nutshell is an endocrine problem that leads to excessive self-creation of steroids on the part of the animal. These excessive steroids will then cause the immune system to not work well and allow simple scrapes to turn into big infections – and thus an itch. Diagnosed by further testing, Cushing’s can be successfully treated by either trilostane or mitotane. Determining the cause of the itch is not insurmountable. However, it does take patience, a very thorough history, and more patience. One thing to remember with skin issues is that they can require a lengthy game of CSI to fix the problem – it might take some time on the part of the vet and client to solve the riddle. Quick fixes are usually just that; a short relief for your pet before the itching recurs. If we want to do our best to eliminate and prevent recurrence of that dreaded itch, we need to take our time and do it right.