Every spring, allergy sufferers turn their thoughts—not to love—but to antihistamines. The yearly onslaught of pollen, grasses, and trees makes some dogs miserable, too. The result: atopy, a skin disease that causes extreme itching.
What causes allergies? Some people and dogs develop antibodies that fight allergens inhaled or absorbed through the skin. These allergens can include those mentioned above, as well as mold spores, housedust mites, and dead skin cells.
Atopy is quite common; in fact, 10 percent to 15 percent of dogs suffer from allergies.
Risk factors and detection
Atopy affects all dog breeds. But beagles, Boston terriers, Cairn terriers, Shar-Peis, Dalmatians, English bulldogs, English setters, golden retrievers, Lhasa apsos, miniature schnauzers, Scottish terriers, West Highland white terriers, and wirehaired fox terriers are more allergic than other breeds.
Climate also plays a big role, even among predisposed breeds. Humid, warm climates lead to a longer allergy season with high pollen or mold-spore levels.
Because an animal must be exposed repeatedly to an allergen before atopy symptoms appear, veterinarians rarely see the disease in dogs younger than 1 year old. Most dogs show symptoms before they turn 7 years old.
Signs of atopy include:
- persistent licking or chewing, especially the paws
- scratching many areas of the body
- rubbing the face or ears
- head shaking
- red eyes
- occasional sneezing.
Often the medical history, clinical signs, and physical exam findings suggest atopy, but your veterinarian may want to perform additional tests to support the diagnosis and rule out other skin diseases. These tests may include skin scrapings, examination of skin cells under a microscope (cytology), and fungal cultures. In addition, if your veterinarian feels that immunotherapy (using drugs to alter the immune system) is the best treatment for your dog, he or she may refer you to a veterinary dermatologist for an intradermal skin test. Allergy tests using blood are also available, but they're less accurate.
Symptoms appear seasonally at first, but tend to last longer as the dog ages and allergies worsen. The incessant urge to scratch or lick often leads to more serious skin infections. Occasionally, a dog may scratch or lick himself until he bleeds. These "hot" spots are called pyotraumatic dermatitis and require immediate veterinary care.
Prevention and treatment
The only cure for atopy is to remove the offending allergen. But short of moving to a different geographic region, you can't get rid of many allergens, including mold and pollen. In mild allergy cases, your veterinarian will manage the disease by alleviating the symptoms.
Antihistamine and fatty acid therapy may help if your dog's atopy is a new condition or seems mild. Not every dog responds to the same medication, so you may have to try several antihistamines. Your dog's doctor also may help control the itching with medicated shampoos. Combined, these methods relieve 10 percent to 50 percent of affected dogs.
Antihistamines can cause drowsiness in dogs, just as they do in people. In rare cases, dogs become hyperexcitable or irritable. Report any side effects to your veterinarian so he or she can adjust the dosage or suggest another antihistamine.
Corticosteroid treatment, which includes corticosteroid injections or pills, may help dogs who don't respond to antihistamines. These treatments are more effective than antihistamines, but they also cause more side effects, such as adrenal gland suppression; immune system suppression; and increased appetite, thirst, and urination. (Occasionally, dogs will urinate in the house.) Corticosteroids are best used intermittently in low doses, preferably given every other day and for a limited time.
With pills, your veterinarian will start with a higher dose, then gradually wean your dog because of the side effects. This may take a month or longer. Injections last longer, which means you don't need to administer a treatment daily. Injections may be more convenient, but they're also more dangerous. As always, report any side effects to your veterinarian.
Immunotherapy is the best choice for moderate to severe atopy cases. To begin immunotherapy, your veterinarian will refer you to a veterinary dermatologist who will determine which allergens cause your dog's misery. Once the dermatologist identifies the culprits, he or she will develop an injection to help desensitize your dog to the allergens.
Immunotherapy helps 60 percent to 70 percent of patients, without the serious side effects associated with corticosteroids. However, it does take three to six months to see a response.
At home, practice strict flea control—flea bites can make your dog's itching even worse. Also, avoid exposing your dog to allergens, such as house dust, feathers, and tobacco.
Prognosis
Atopy is a lifelong disease. The condition isn't fatal, but if left untreated, your dog's symptoms will worsen and last longer each consecutive year—making your dog miserable and putting him at risk for developing skin infections. Timely therapy helps ensure your dog lives a happy, comfortable, and healthy life.
