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Pender Veterinary Centre

4 Reasons Your Dog May Be Scratching

Dog getting combed for fleas

An itchy dog is one of the most common patients seen by veterinarians.

The constant nighttime jingle of a scratching dog’s collar will try the patience of even the most loving owner. Being itchy all the time would make anyone miserable, and we want our canine friend to be comfortable, even if it means a trip to the vet.

Why and how dogs itch

Many dogs are itchy because of environmental allergens like pollens, molds and dust mites. People sneeze, cough and rub their eyes; dogs scratch. Dogs can also be itchy when they have food allergies. Most itchy dogs have at least some allergic component to their problem. Other diseases can make a dog itchy, however, and these other causes should be ruled out before declaring a dog allergic.

Itchy dogs scratch. They also lick themselves excessively, bite and chew at their flanks or extremities, rub against furniture, run their faces or shoulders along the carpet, scoot on their bottoms, or roll in the grass. They may lose hair or develop secondary infections from the damage they do to their skin.

Primary infection

What came first, the chicken or the egg? Does my dog have a skin infection because he itches, or itch because he has a skin infection? Usually the itch comes first. But dogs can have a bacterial or yeast infection as their primary problem. Primary skin infection is more likely when a patient has a weakened immune system from hormonal disorders like low thyroid function or an overactive adrenal gland. Bloodwork is necessary to diagnose these diseases. Fungal infections like ringworm, also more common in immunodeficient patients, is diagnosed by skin culture.


Fleas are a common source of itching. For unfortunate dogs allergic to flea saliva, the bite of even one flea is enough to cause frenzied scratching. Late fall is the most common time of year for dogs to be obviously itchy from fleas. Year-round use of either topical or oral flea products will prevent flea infestations. Once fleas are established in your environment, erradicating them can be difficult and expensive, so it is wise treat your pet for fleas before you see them.

Mites and other bugs

Scabies is caused by a microscopic mite (Sarcoptes scabiei) which burrows into the skin and causes intense inflammation. Dogs sharing a yard with foxes, even if they are never in it at the same time, may be exposed. Mites can also spread through contact with other affected dogs or with poorly cleaned brushes at a careless grooming facility. Mites are usually detected by scraping the top layers of skin with a sharp blade and examining the scrapings under a microscope. They can be hard to find, so veterinarians may treat a very itchy dog for scabies just to rule out that disease as a possibility. Treatment usually involves a medication administered every two weeks for three to four doses.

Demodicosis is caused by a different type of mite. Demodex mites are normally found in low numbers in the hair follicles of healthy dogs. In young animals with immature immune systems or in older patients with underlying disease, mite populations can begin to proliferate out of control and cause damage. Demodex-invaded skin is ripe for bacterial infection.

Dogs can also be itchy from infestations of ear mites, lice, chiggers or Cheyletiella mites. Fortunately with the routine use of flea prevention products, many of these diseases are now uncommon.

More serious skin disease

Sometimes itching is the result of cancerous invasion of the skin. Lymphoma and malignant histiocytosis are two cancers that may manifest in the skin. Immune-mediated disease, where the body essentially attacks its own cells as if they were foreign, can also result in skin lesions that are itchy. Fortunately these causes of itching are rare, but skin lesions that are not responding to treatment for more common problems may warrant taking a biopsy for microscopic analysis.

Finding the cause

When your itchy dog first goes to the veterinarian, medicines or shampoos may be dispensed for symptomatic control of the itch. If the itch persists or recurs, skin scrapings for mange mites, skin cytology to look for bacteria or yeast, and a fungal culture for ringworm are warranted. If these tests are negative, then perhaps the problem is food or an environmental allergy. If treatment for allergy is ineffective, however, therapeutic trials to rule out infection, flea allergy or mites may be recommended. Bloodwork may be necessary to rule out underlying systemic disease. In some extreme cases, skin biopsy may be needed.

Scratch, scratch, scratch — your itchy dog is unhappy. While the solution to his problem may not be a quick and easy diagnosis, you owe it to him to try. Not only will he be more comfortable, but you may finally be able to get a good night’s sleep.