Dogs are taken to the veterinarian for skin problems more than any other reason. Most often they are itchy and that itchiness is typically due to allergies. The text of canine and feline dermatological diseases is large because there are hundreds of skin diseases; however, it can help to start with some generalities when determining the cause.
Again, there are many causes of itchiness, but allergies are one of the most prevalent causes. The most common allergies are flea allergy, food allergy and atopy, which is an allergy to environmental allergens, especially pollen, molds, and house dust mites (which are in all houses). The location of the lesions and itchiness, as well as seasonal patterns, can give clues as to the type of allergy.
Flea allergies are very common. With this allergy, pets are usually most itchy in the back half of the dog. Commonly there is hair loss, redness, and possibly scabs and superficial infection over the dog's hips and tail base. You may not even see fleas! If a pet is allergic to fleas, all it takes is one flea bite to make the dog itchy for 2 weeks. When the pet is licking and chewing at itself, he or she often eats the flea which then destroys the evidence. The flea bite has still set off an inflammatory response so the pet is still itchy. Veterinarians seeing dogs with lesions in these areas will suspect a flea allergy even if they don’t see any fleas.
Food allergy is also a common allergy. Dogs generally show food allergy symptoms in their ears, face, feet, or rear. Pets don't become allergic to a brand, they are allergic to one or more ingredients. Thus just changing brands of food probably won't help the itchiness. The most common food allergens are beef, dairy products, chicken, lamb, fish, chicken eggs, corn, wheat, and soy. To make matters more difficult, research shows that that in the manufacturing process of pet foods, there is a lot of cross contamination of ingredients. This means there are ingredients in the food that are not on the label. There is no valid blood or skin test to determine if your pet has a food allergy, but your veterinarian can help you find a food to use as a trial. Food trials last 2 to 3 months, during which only the recommended food should be used (no other food items, treats, etc) to determine whether your pet has a true food allergy. It should also be noted that our patients with food allergy frequently have atopy (environmental allergies) as well, so you may not see a complete resolution of your pet’s allergy with a dietary trial alone. For those complicated cases, frequent communication with our veterinarians will help determine the efficacy of a food trial.
Atopy, the allergy to such environmental things as pollen, house dust mites, and molds, frequently causes the dog to be itchy in the face or feet, but they may seem to be itchy “all over”. Unfortunately this type of allergy can be harder to control because it is often not possible to totally remove these allergens from the pet’s life. Many dogs will have seasonal atopy and only need occasional symptomatic treatment. Other patients may have more severe atopy (e.g. allergic to something constant in the environment, or allergic to many different allergens). Our veterinarians can help you decide if symptomatic care is appropriate for your pet, or if other modes of allergy treatment/diagnosis are better. Other modes of treatment can include chronic medications (cyclosporine, Apoquel, etc) or immunotherapy.
Skin lesions from allergies are frequent as well and can include redness (inflammation), excoriations, and areas of secondary infection. Our veterinarians will check for any secondary skin infections as these will make the dog itchy even if you get rid of the allergen from the dog's environment. Our veterinarians can help your itchy dog; since this the most common complaint we see, we have lots of experience!
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