Why is Scruffy scratching?

It used to be that flea-allergy dermatitis, which is an allergic skin reaction to flea bites, was the most gnawing concern of pet owners. But with the advent of more effective flea-control products, the incidence of flea-related allergies has declined dramatically, says Lowell Ackerman, a veterinary dermatologist who is dermatology course director for Tufts University Cummings School of Veterinary Medicine in Boston and author of several books on skin disorders in animals.

Taking their place as the greatest causes of itching and scratching in pets are environmental, or inhalant, allergies and food allergies. Environmental allergies are usually caused by airborne allergens such as grasses, weeds, mold and dust mites. Common ingested allergens are proteins such as beef, chicken, soy and carbohydrates such as corn or wheat.

Environmental allergies are extremely common in dogs, Ackerman says, affecting as much as 15 percent of the purebred dog population. These types of allergies are often seasonal, simply because there are seasonal variances in what they react to.

Doc, a golden retriever, experiences allergy flare-ups every fall after the heat goes on in the house, despite a humidifier on the furnace, says his owner, Nona Kilgore Bauer, of LaBelle, Mo.

"If there is an allergy to a solitary seasonal pollinator, such as ragweed, the clinical allergy is also seasonal," Ackerman says. "However, many dogs and cats have a combination of seasonal and nonseasonal allergies, which may give year-round allergy problems, but with seasonal spikes. If animals have food allergies, the problems are typically year-round, but there may also be seasonal spikes if there are concurrent inhalant allergies, which is not uncommon."

Certain breeds most at risk
Allergies also have a heritable component and tend to occur more often in certain families or lines of dog breeds - something to ask about before you purchase a puppy. In general, however, the breeds most likely to develop allergies are golden retrievers, virtually all terriers, Dalmatians, Chinese shar-pei, Labrador retrievers, boxers and bulldogs.

Allie is a golden retriever who has issues with food. "We got Allie in December 2002, and within a few months she began suffering from near-continuous infections in both ears," says her owner, Susan McCullough, of Vienna, Va. "None of the conventional treatments helped for very long. Within a week or two of getting rid of one infection, a new one would set in. Our vet suggested that Allie be tested for food allergies."

McCullough put Allie on a commercial elimination diet of venison and potato - ingredients she'd never eaten before. After four months, Allie's ears cleared up. Rather than put Allie through the challenge phase of the elimination diet, which involves adding in the foods she'd eaten previously to figure out which one caused the problem, McCullough and her veterinarian agreed it would be best to simply keep her away from those foods (duck, sweet potato, wheat, corn, beef and chicken). Allie now eats a varied diet that includes such ingredients as pork, quail, rabbit and fish.

Allie is a rarity, though. Percentage-wise, cats have more food allergies than dogs, says Kim Boyanowski, a veterinary dermatologist at Peninsula Animal Dermatology in Redwood City, Calif. "Cats usually distinguish their food allergies on their skin a little differently than dogs, so it's more on their head and neck and ears, where dogs can have food allergies manifest on other areas as well," she says.

When people have allergies, they sniffle and sneeze. Pets are more likely to scratch, lick and chew in a vain attempt to quell the intense itching sensation. They lick and chew their paws until they're wet, red or raw, rub their faces on the carpet, scratch frantically at their ears, and develop rashes in armpits and groin areas. Factors such as recurrent skin infections, the location of allergy signs, the breed of the patient, and the age of onset can all help your veterinarian confirm a diagnosis.