Dear Spring Oaks’ Family:

The May topic of the month is canine skin problems.

There are not many things more frustrating than a dog that will not stop scratching.  How do we make him stop?  By first identifying what is making him itch in the first place.  This can be difficult.  Many causes of skin problems make the dog react in the same way, by itching.  The itching initially makes the skin red.  The damage caused to the skin can allow bacteria and yeast into the skin causing red bumps, pimples, and scabs.  Chronic problems can lead to greasy or dry coats, thickened skin, and a darker appearance to the skin. 

The first thing we typically look for are external parasites, fleas and mites.   Fleas are the most common cause of skin disease in dogs.  They bite the dog to suck blood and when they do saliva gets into the wound.   This flea saliva is quite irritating to the dog and can cause itch long after the flea is gone.  Sometimes fleas are easy to find.  The most common place to find them is near the base of the tail, low back, and the rear legs.   The presence of flea feces (“Flea Dirt”) is also evidence the skin problems are due to fleas.  Flea dirt looks like small black pieces of dirt but when moistened it dissolves with a red color identifying it as digested blood.  Even if we do not find fleas or flea dirt, fleas may be suspected as the underlying cause of the skin disease due to the pattern of hair loss or if the pet is not on adequate or timely flea control.  Here in Florida we recommend year round flea control for all pets regardless of whether fleas are seen or not.  Flea control for dogs includes: monthly Comfortis, a combination of flea control and heartworm prevention called Trifexis or monthly Frontline,  Flea control for cats includes: monthly Frontline or Advantage Multi.

The two most common types of mites that can cause skin problems are Demodex and Sarcoptes.  Demodex mites are a normal inhabitant of dog skin but are usually in low numbers and do not cause a problem.  These mites can multiply in number and cause skin problems if the dog has intestinal parasites, poor nutrition, stress, or anything that would cause a decrease in the immune system’s ability to function.  Demodex is not contagious to other dogs.  It is most commonly found in young puppies.  Sarcoptes are mites that burrow into the skin.  Dogs with scabies often have been to an animal shelter, contact with stray dogs, or contact with strange dogs.  Scabies is contagious to other dogs and people.  Mites are diagnosed through skin scrapings.  A dulled scalpel blade is used to abrade the affected area and the removed hair and skin cells are examined under the microscope for the presence of mites. 

Infections also contribute to skin problems.   There are two types of infections, primary and secondary.  Dermatophytosis (Ringworm) is a primary fungal infection that occurs in many species of mammals including people.  It is called ringworm due to the ring like lesion produced on human skin.  Some strains of ringworm will glow with an ultraviolet light but other strains do not.  A definitive test is conducted by putting some potentially infected hairs into a special culture media.  If a white fuzzy growth is produced and the media turns red the results are most likely positive.  Confirmation is made by looking at the fungus under a microscope.

The most common secondary infections are caused by Staphylococcus bacteria and Malassezia yeast organisms.   These organisms normally live on the skin in low numbers.  The skin serves as a barrier, keeping them on the surface.  When a dog itches, it breaks the barrier of the skin and allows these organisms to colonize underlying layers.  Certain types of lesions on the skin may make us more suspicious of a secondary infection.  The doctor may use a tape preparation to confirm the suspicion by finding yeast or bacteria under the microscope.  We typically treat the secondary infection because it contributes to the itching of the skin but the infection is almost always secondary to an underlying problem which needs to be identified and treated as well.

 Allergies are blamed for many skin conditions in animals, and many animals do in fact have allergies.  The key is to establish a definitive diagnosis by ruling out other causes of skin problems prior to performing testing or treatment trials for allergies.  Once parasites and infections have been excluded we can consider the main types of allergic disease, food hypersensitivities and environmental hypersensitivities (atopy).  There are a few general characteristics of each type which may help us narrow our suspicions.

Food hypersensitivities tend to occur year round.  The most common areas of skin problems are ears and around the anal opening.  Food hypersensitivities occur due to repeated exposure to the same ingredient, usually the protein source.  We do not know why this occurs as many dogs and cats can happily eat the same food their entire lives without issue.  Just changing brands of pet food rarely helps as many ingredients are common to many pet foods.  Blood testing for food hypersensitivities is inaccurate and should not be done.  The only way to definitively diagnose food hypersensitivity is to do a diet trial with a Limited Ingredient Diet or Hydrolyzed Diet.  It may take 6 to 8 weeks to see a response.

Environmental hypersensitivities (atopy) usually start between the ages of two and five years.  They tend to be seasonal initially and the most common areas of skin problems are the feet, facial area, ears, armpits, and front of the elbows.  Atopy is a diagnosis made on the presence of clinical signs and history once all other causes of skin disease have been rules out.  There are two ways to definitively manage atopy, desensitization injections and Atopica.  Desensitization injections are similar to the “allergy injections” given to people.  The grasses, weeds, tree pollen, molds, and dander the pet is allergic to is determined by a skin test or blood test.  Once this information has been obtained an allergy extract is formulated for injection.  Approximately 60-70% of dogs with atopy will respond to desensitization injections.  It is not a quick fix though and can take several months to see results.  Some dogs will still require other topical and oral medication, shampoos, and special food to manage their itching.   Atopica is an oral medication licensed to treat atopy in dogs.  It works on the immune system to reduce the allergic response.  It may cause some minor gastro-intestinal distress when first starting the medication but has virtually no long term side effects. 

Regardless of the cause of the itching, your veterinarian will likely recommend treatment with antihistamines such as Benadryl, Claritin, or Zyrtec.  These medications are a mainstay of therapy for people with itchy skin and allergies and they are thought to help dogs as well.  Just like with people, dogs may respond to one antihistamine better than another.  We also will likely recommend topical therapy with a medicated shampoo, foot wipe, or medicated spray.  Topical therapy can target certain organisms such as bacteria or yeast and can moisturize the skin, be degreasing to the coat, or sooth itch.  The products recommended will be targeted to your individual pet’s need.  We may also recommend dietary therapy.  Diets for food hypersensitivity have already been mentioned, but we may also recommend a diet such as Royal Canin Skin Support which contains a high level of omega-3 fatty acids for inflammation and the PINCH cocktail to help strengthen the skin and reduce water loss.

Skin disease in dogs and cats can be frustrating but by following your veterinarian’s recommendation your pet’s quality of life can be greatly improved.  Sometimes the skin disease can be cured and sometimes only controlled, but regardless there is a good chance we can help stop that itch. 

Sincerely,

Dr. Jim Jackson