Canine Allergies

What are allergies?

An allergy is an abnormal reaction of the immune system. Normally, the immune system fights off foreign agents like bacteria and viruses to protect the body. In an animal with allergies, the immune system is reacting in an abnormal way to substances like pollens, dust, mold, fleas, or certain foods. An allergy to inhaled particles, like dust or pollens, is called “atopy“.

What are symptoms of allergies in dogs?

Most dogs with atopy get itchy skin. They may lick their feet, rub their faces and/or scratch their bodies. The skin may get red and irritated, and skin infections may occur because of the scratching and trauma to the skin. Eventually, the skin may be chronically irritated and be thick and leathery in certain areas. Other common symptoms include recurrent ear infections, greasy or flaky skin, or hair thinning. Dogs may less commonly have irritated eyes or nasal discharge.

Food allergies frequently have the same symptoms as atopy, but some dogs also have digestive upset such as vomiting or diarrhea.

Dogs with flea allergies usually have itchy, inflamed skin, particularly on the back near the tail.

How are allergies diagnosed?

Atopy is diagnosed by evaluation of the symptoms and response to treatment, and skin or blood tests are done to determine exactly what the dog is allergic to. These tests are necessary prior to hyposensitization treatment (see treatment section below). Food allergies can have the same symptoms as atopy but require a hypoallergenic diet trial to diagnose them (see treatment section).

How can allergies be treated?

1. Dogs with allergies should be on a flea preventative, as they are frequently highly allergic to fleas. Keep allergic pets away from other biting insects as well, if possible.
2. Monitor carefully for any circumstances that seem to increase your dog’s symptoms, such as swimming, warm humid weather, certain foods or treats, shampoos, medications, season of year, use of a woodstove, etc. Knowing what worsens your dog’s symptoms can allow you to avoid those situations and can help make the diagnosis.
3. Keep the skin and haircoat clean and brushed– this allows you to monitor the skin condition more easily and reduces the likelihood of infection. In some situations specific shampoos, wipes or topical products may be advised.

Specific Treatment for Atopy

1. Antihistamines can help reduce the symptoms. Some dogs are sleepy when first started on antihistamines, but this side effect usually goes away after a few days. These are safe for long term use. Keep in mind that antihistamines need to be given regularly, often several times a day, in order to be effective. It may take a week or longer to see improvement after starting these medications. These medications are available over-the-counter, but be sure to use products that contain only these ingredients — many multi-symptom products for humans have other ingredients that are not safe for dogs.
2. Fatty Acid Supplements: Omega 3 fatty acid supplementation can reduce skin inflammation in dogs. This natural product, derived from fish oil, is very safe. It is usually easiest to feed a diet formulated to have the appropriate omega 3 ratio, rather than to supplement with fish oil capsules. Non prescription foods such as Science Diet Sensitive Skin and Stomach may be recommended for some cases of atopy. In other situations prescription diets may be advised.
3. Limit exposure to allergens — many dogs have most severe symptoms in spring or fall, and keeping the air conditioner on can help filter the indoor air at these times. Change filters in air conditioning units and furnaces frequently. For dogs with allergies to dust or dust mites, removing or vacuuming carpeting frequently and washing curtains can reduce household dust.
4. Cytopoint is an innovative new injectable therapy that targets itch at its source lasting 4-8 weeks per injection. This injection works by specifically neutralizing one of the main proteins that sends the itch signal to the brain. This is a very safe and effective treatment with low risk of side effects.
5. Apoquel is an oral medication that stops itch at its source regardless of the type of allergy. It begins relieving itch within 4 hours and effectively controls the itch for 24 hours. Apoquel can be used long term if needed for continued itch relief. In studies, the side effects from apoquel were mild and similar to those seen with placebo (sugar pills).
6. Corticosteroids — Drugs like prednisone are usually very effective in reducing itching related to atopy. A short, tapering course of prednisone (or sometimes a single injection) can be used to control severe itching. However, long term use of corticosteroids is not usually recommended, due to side effects that can occur with continual usage (elevated liver enzymes, increased risk of diabetes). Short term use is generally safe, although some animals will show side effects such as increased thirst, increased urination, and increased appetite. These side effects will go away once the dosage is reduced or discontinued.
7. Hyposensitization Therapy — “Allergy shots” or a newer version of hyposensitization therapy in the form of a drop under the tongue (sublingual allergens) are used to train the immune system to respond more appropriately to the allergens in the environment. This process starts with testing to determine what the animal is allergic to, and then the owner is taught to either give injections or use allergen drops under the tongue on a regular basis at home. This treatment is usually continued for months or years or life long, depending on the animal’s response. For testing, the patient needs to be off of some of their allergy medications for 6 weeks and it is best to do the test during the time of year that symptoms are the worst. Hyposensitization therapy is the only treatment that can decrease the immune system’s response to the offending allergens leading to long term improvement in how the body responds to allergens.
8. Antibiotics are frequently needed to control secondary bacterial infections of the skin, often caused by excessive chewing or licking. Medicated shampoos, wipes or topical products may also be used to help reduce or prevent secondary infections.
9. Yeast infections can also occur secondary to atopy, and antifungal treatment may be necessary.

Diagnosis and Treatment of Food Allergies

1. In animals that are suspected of having food allergies, a hypoallergenic diet trial is necessary to diagnose this condition. The animal is placed on a special diet that does not contain any ingredients that could be triggering allergies. Usually a minimum of eight weeks is needed for a diet trial. It is very important that the dog not be given any other foods during the trial, as even a small amount of an allergenic food could make the dog itchy. No treats, rawhides, beef flavored heartworm preventatives, etc. should be given during the trial. If the dog has food allergies, the symptoms should improve during the trial, but this may take several weeks to see improvement.
2. After the diet trial, different food items are slowly introduced to see what foods the dog can tolerate, and which cause problems.

Allergies in dogs are frequently a lifelong disorder, but most dogs can lead comfortable, normal lives with treatment. It can take trial and error to find the right combination of therapies each pet will need to control their symptoms as all pets allergies are different. Working closely and openly communicating with your veterinarian is the most successful strategy in managing allergies.