That Doggone Itch!

By Naomi Keiper DVM

One of the more common reasons for dogs to visit the veterinarian is itchy skin. Pruritus (itch) can be a frustrating condition for both owners and veterinarians due its many complex underlying causes and the challenges in achieving adequate control in some dogs.

Every patient presenting for itch is unique and there is not one correct solution that will work for every dog. It may take time to find a treatment combination that best addresses your dog’s specific issues.

When presented with an itchy dog a veterinarian will take a systematic approach to diagnosing the disease. Two of the most important steps in this approach are obtaining a detailed history from an owner and performing a thorough, full-body physical exam.

Next steps may include skin scraping and cytology (examination of cells under a microscope) to look for external parasites, the presence of bacteria and the presence of fungal organisms. At the same time fecal testing, blood work and urinalysis may be recommended on a case-by-case basis.

If no infectious organisms are apparent from the above testing your veterinarian may still treat for fleas, even if they were not directly observed. Fleas can be a major trigger for itch in dogs and their removal/prevention will facilitate a more comfortable dog. Many dogs with strong reactions to fleas have a condition called flea allergy dermatitis (FAD). In dogs with this condition the animal is allergic to the saliva of the flea, which elicits a full-body immune response that can last for weeks after an initial bite, causing long lasting itch.

If a secondary bacterial or fungal skin infection is present, your veterinarian will treat for this before instituting other treatments. Secondary infections often arise due to a poorly functioning or abnormal skin barrier. A dog’s skin provides a wall to the outside world, defending internal systems from a variety of insults including bacteria, fungal organisms, external parasites, pollen, chemicals and other irritants. Dogs with itchy skin often have an underlying disruption to their skin barrier, which makes them more susceptible to secondary infections. Treatment with an oral and/or topical antibiotic until infection has cleared will be used as necessary.

Once external parasites and secondary bacterial or fungal infections are controlled, one of the next steps in diagnosing the itchy dog is a diet trial to assess for food allergy. Strict diet trials can identify components of food that should be avoided for an individual dog.

The majority of dogs are allergic to the protein source (ex. chicken or beef) rather than the grains within a food. Diet trials can be accomplished by feeding a novel protein diet (ex. Kangaroo or bison) or by feeding a prescription hypoallergenic diet. Diet trials can be challenging because even a single bite of what the dog may be allergic to, either in a treat or dropped morsel of food, will necessitate starting the trial from the beginning.

If a dog remains itchy despite trying the therapies/approaches listed above then a diagnosis of atopic dermatitis may be made. Atopic dermatitis is a chronic hypersensitivity condition that causes itchy inflammation of the skin and ears. Atopic dermatitis cannot be cured however it can often be controlled for the life of the patient.

Animals with atopic dermatitis have an abnormal skin barrier (leading to sensitive skin and a higher likelihood of developing secondary infections) and an overactive immune system that will overreact to certain triggers. Triggers may include: dry skin, food allergy, fleas, infection and environmental allergens. Allergen specific immunotherapy is currently the only available method for improving a dog’s immune health. This therapy involves exposing an animal to very small quantities of environmental allergens to which the individual is specifically sensitive (ex. dust mites or birch pollen) though the use of subcutaneous injections or sublingual drops.

When further treatment is deemed necessary to address atopic dermatitis, a multi-modal approach is often used that may include the use of antibiotic/antifungal shampoo, grooming, antihistamines, omega 3/6 fatty acids and immune modulatory drugs.

Immune-suppressive drugs like steroids are often the least expensive option but should be avoided if possible due to their unpleasant side effects and potential harm to organs with long-term use. However, other immune-modulatory drugs may be great options for your pet. These drugs, in contrast to steroids, more specifically target parts of the immune system directly involved in itch and thus have fewer side effects.

In conclusion, itch in dogs can be simple to treat but can also be a sign of a complicated disease that will require extensive long-term treatment. Every itchy dog is assessed as an individual to create a patient specific treatment plan. It is important to remember that working closely with a veterinarian over months or years and being open to treatment changes will be the best approach to making an itchy dog as comfortable as possible.