When your dog pumps its leg frantically to scratch its ear, or your cat bites its tail furiously until the fur falls out, it's clear that your pet is itching for relief.

Occasional scratching is normal, but if a pet scratches or bites itself relentlessly, a health problem may be the cause. Itching can be triggered by a variety of conditions, ranging from liver disease to lice, from fungus to fleas, from mange to anxiety.

But the leading cause of itching and scratching in pets is allergies, says Linda Messinger, D.V.M., a board-certified veterinary dermatologist at the Veterinary Referral Center of Colorado in Englewood. "Allergies are also the most common underlying cause of ear problems in dogs," she adds.

Unlike people with allergies, animals don't usually get stuffy or runny noses or watery eyes. Their main symptom is itchy skin, which can turn raw and red from scratching, licking, and chewing. This condition is called allergic skin disease, or allergic dermatitis. With enough scratching and biting, open sores can form, creating a haven for bacteria or yeast that can lead to infection.

"Just about every mammal can get allergies," says Lisa Troutman, D.V.M., a veterinarian with the Food and Drug Administration. "So can hamsters, rabbits, birds, and some other pets." But dogs and cats are the pets most frequently seen with allergies.

To relieve the itch, dogs may scratch and bite at themselves and rub their face with their paws or against the floor and furniture. "Cats tend to pull out their hair and get patchy hair loss on their ears, legs, and around their eyes," says Troutman. "They'll make themselves bald."

There is no cure for allergies. "They are a lifelong problem," says Messinger, "and oftentimes they get worse as a pet gets older."

But there are treatments to relieve itchiness, clear up infections that arise from constant scratching, and even "desensitize" a pet to substances that cause allergies. In addition to regulating drugs for people, the FDA regulates drugs for animals, and the agency's Center for Veterinary Medicine has approved medications to treat itchy pets and their infections.

The key to making your pet comfortable is to find out the cause of the itchiness. If the pet is allergic, determining the source of the allergies will help with treatment, says Messinger.

Types of Pet Allergies

Allergies that can plague pets are grouped into four types: flea, food, atopic, and contact.

The most common type of allergy in both dogs and cats is flea allergy. The offending allergen is actually the protein in flea saliva left in the skin after a fleabite.

Atopic, or inhalant, allergy is the second most common allergy in dogs and the third most common in cats. Breathing in or directly contacting airborne particles in the environment, such as mold spores, dust, tobacco smoke, and pollens, will activate atopic allergies.

If a pet is allergic to pollens, it will show symptoms even if you keep it indoors, says James Jeffers, V.M.D., a board-certified veterinary dermatologist at the Animal Allergy and Dermatology Clinic in Gaithersburg, Md. Outside airborne substances waft their way into the house, and air filters don't tend to bring relief to pets with these types of allergies, he says.

Although pets with atopic allergies sometimes have respiratory problems, such as coughing and sneezing, they more typically develop itchy skin. Certain dog breeds are more likely to develop atopic allergies, including terriers, Dalmatians, and golden and Labrador retrievers.

Food allergies are the second most common type of allergy in cats and the third most common in dogs. Food ingredients most likely to trigger allergies in cats are fish, milk, beef, and eggs. Ingredients most likely to cause a reaction in dogs are beef, soy, chicken, milk, corn, wheat, and eggs. Some pets with food allergies may have vomiting and diarrhea.

A reaction to physically touching a substance is called contact allergy, the least common type of allergy in dogs and cats. Contact allergens include grass, wool, and plastic. Jeffers occasionally sees dogs in his clinic with "plastic dish dermatitis," an irritation to the skin on the nose caused by a reaction to an antioxidant found in a plastic food or water dish. The condition clears up when the pet is switched to a metal or ceramic dish. And although uncommon, some cats become allergic to kitty litter, says Jeffers. But allergies caused by contact with chemicals, such as those contained in cleaning fluids, waxes, carpet cleaners, and lawn fertilizers, are "about 1 in a million," he says. Nevertheless, these products are potentially toxic, and pets should be restricted temporarily from areas treated with them.

An Itch for All Seasons

Some pets' allergies are set off by seasonal changes. Springtime, with its tree pollens, brings on the animal form of hay fever, which is primarily itchy skin. Mosquitoes and flies, which may trigger allergies, are rampant in summer. Grasses and flowers often release pollen in summer and late-blooming plants produce pollen in early fall, creating airborne irritants. Fleas and the allergies they activate persist in spring through fall in most parts of the country, but are found year-round in some areas.

Geography also plays a role in allergic reactions. Regional changes mean different varieties of grasses, trees, insects, and other environmental elements, which can affect allergies. Jeffers says when he took his dog camping in Maine, the pup was healthy, but when he brought him back home to Maryland, he started itching.

Tags: Pets

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