Dogs are susceptible to the same variety of allergy triggers as humans — foods, inhalants, and contacted substances. They can also be allergic to fleabites (as can humans). Determining the precise cause of an allergy is often difficult and time-consuming. The exact symptoms caused by the allergen may suggest one cause over another, and treatment can be based on that suspicion. Improvement indicates a correct choice.
Your veterinarian might suggest taking skin scrapings or doing intradermal testing (injecting possible allergens under the skin) to try to pinpoint allergy causes. This is a reasonable course of action, but be aware that it doesn't always result in definitive answers.
Don't be in denial about possibly having a flea or two on your dog or in your home. These little pests haven't managed to exist through history because they're easy to kill. Instead, confront the problem using one of the good flea preventives available, and check often for signs of fleas. One good way to check for the presence of fleas is to brush your Yorkie's underside — the stomach and between the hind legs — then clean the comb out onto a moistened white paper towel. Flea dirt consists mostly of dried blood, and if it's present, you'll see red spots on the towel.
In dogs that have a flea allergy, a single fleabite could be enough to cause chewing and scratching. Most of the chewing will center on the base of the tail and between the hind legs. This condition can worsen quickly and cause hot spots, or raw, irritated patches of skin.
Spot-on flea products also kill ticks, which is certainly a bonus if you live in tick territory. Some of these products claim to take care of mosquitoes as well. Ask your veterinarian for advice on which brand and type of product to use.
The ultimate solution is to keep your dog and home flea-free. While this does take some effort, it's much easier than it used to be. Consult your veterinarian about a spot-on product for your Yorkie — the active ingredient kills fleas but has no effect on mammals — and a combination pyrethrin/IGR spray for your home. The pyrethrin is a toxin, but it kills fleas and then quickly degrades into harmless by-products. The IGR is an insect growth regulator, preventing flea eggs from hatching or larvae from developing, and is entirely safe for mammals.
While you are gaining control of the flea problem, you may need to also take action to help your Yorkie cope. Rather than using a flea shampoo, which is harsh, use a spot-on treatment and a soothing medicated or oatmeal shampoo to help calm the skin. Your veterinarian may suggest some antihistamines to make life easier and let hot spots cool down. Severe cases may even require a short course of steroids.
Dogs develop food allergies over time, so a food that your Yorkie was eating quite happily at one point may cause problems a year or more later. The symptom, again, is itchy skin, but the itch from a food allergy tends to focus on the ears, face, stomach, and back of the hind legs.
If your veterinarian suspects a food allergy, he will probably want to put your dog on an elimination diet. He might recommend a commercial diet with limited novel ingredients (meaning things your dog hasn't eaten in the past), or a homemade diet, usually consisting of lamb and rice. However, there's no longer anything special about lamb. It was once used as the protein portion of a novel-ingredients diet because most dogs had never eaten lamb. Now, with all the lamb-and-rice diets available, other proteins such as duck or venison have to be used.
The dog has to eat only the prescribed diet for several weeks. That means no other treats or snacks can be given, unless they contain only the same ingredients as the prescribed diet. You may be able to find some sort of treat with the same ingredients but in a slightly different form, or you'll have to use the diet as both dinner and treats.
If the allergies improve while on the elimination diet, the proposed diagnosis of food allergies is confirmed. Ingredients are then slowly added, one at a time, in an attempt to find the specific food(s) causing the problem. Wheat, corn, beef, and milk are frequent culprits. Preservatives or artificial colors and flavors could also be to blame. Once the allergy-triggering items are identified, a permanent diet can be recommended.
Dogs can suffer from hay fever, the same as humans. If the itching and scratching is seasonal, suspect a pollen allergy. Use all the same strategies you would use with a human sufferer — install HEPA filters in your home, and stay indoors as much as possible when the pollen count is really high. Ask your veterinarian about giving your Yorkie antihistamines or even corticosteroids if the problem is severe.
Allergy testing in dogs is expensive, time-consuming, and often inconclusive. Details of when the allergy occurs, and observation of where biting and scratching are concentrated can be just as diagnostic.
Though a problem with inhalant allergies is usually seasonal, the biting and scratching are more generalized than with most other allergies. Hot spots often result, which then have to be treated. Dogs with pollen allergies often develop allergies to other substances, such as dust or mold.
Because the problem comes from direct contact with some material, most of the chewing is directed at the feet and underside. Carpeting is often the culprit. Upholstery could also be suspected if your Yorkie is allowed on the furniture. Many people choose to remove their rugs as a response to the problem.
Dogs can also be allergic to other substances with which they come in contact. Shampoo is one possible cause. Because Yorkies are bathed often, this is an important point to consider. Other triggers might be plastic food and water dishes, which can cause discomfort around the muzzle, or flea collars, which can cause scratching around the neck.
When itching and scratching gets too frequent and is directed at a specific area, the result can be a hot spot. Much of the hair is chewed or scratched away and the skin is warm, red, and swollen. You need to clip away the rest of the hair on the spot and apply medications recommended by your veterinarian. Unfortunately, this can be a painful procedure for the dog.
To keep the dog from continuing to bite at the same or a nearby spot, you may need an Elizabethan collar — a cone-shaped plasticdevice that attaches around the neck and extends around the head — or the newer BiteNot collar — a rigid neckpiece that doesn't allow the dog to turn his head. To stop scratching, you may need to put socks over the dog's rear feet.
Can't you just cover the hot spot rather than use that awful Elizabethan collar?
Unfortunately, this will not work. Covering a hot spot will only keep it moist and encourage bacteria to breed. You have to leave it open to the air for it to heal, and a dog with free range of motion will not be able to resist the temptation to chew.