Scratching and Biting the Skin
A dog that is itching, rubbing, and scratching is an uncomfortable dog. Along with the discomfort, the pruritus (itchiness) may be a sign of underlying problems, such as allergies. The skin itself is an important first-line barrier against bacteria and parasites. Skin that is scratched with tiny cuts is ripe ground for infections. Anything more than an occasional scratch or rub (such as many dogs do right after they eat) is worth investigating.
The most common cause of itching and scratching is the presence of parasites. Fleas, ticks, and various mites can all make a dog extremely uncomfortable. These pests may also carry serious, even life-threatening, diseases, which they pass on to their host dog. (See Chapter 12 for more information on parasites.)
Allergies are another notorious source of itching. With many dogs, food allergies show up as skin problems rather than stomach or intestinal complaints. Inhaled allergies may stimulate a skin reaction as well. Basically if your dog is itching and scratching, has open sores or inflamed skin areas, you should contact your veterinarian. Once parasites are ruled out, your veterinarian may do skin tests or blood work to find the cause of that itch.
Where your dog starts scratching can be significant. A dog with a mild ear infection may rub his ear or even come over and try to get you to rub it. Dogs with allergies often rub their faces and scratch their armpits. Licking or sucking of flank areas may indicate a behavioral problem.