By Lorie Huston, DVM
"Skin disease is the most common reason dogs and cats visit their veterinarian. Hair loss and scratching are two of the most common manifestations of both canine and feline skin disease.
Many different diseases can cause skin disease, but the skin of the dog or cat can only react to disease in a limited number of ways. As a result, many of the diseases that cause skin problems in dogs and cats also cause similar symptoms and look identical to one another.
In order to be able to successfully diagnose and treat your dog or cat for scratching and hair loss, your veterinarian will likely need to perform some basic laboratory testing.
Start the Search for the Cause of Hair Loss and/or Scratching
Your veterinarian will begin the search for the cause of your dog or cat's hair loss by asking you some basic questions. These questions will allow your veterinarian to begin to develop a medical history for your pet.
These are some of the questions you should be prepared to answer:
When did your dog or cat start to lose hair?Is your dog or cat itchy?Has your dog or cat suffered from similar problems in the past? If so, when?Is your dog or cat currently taking any medications? Herbal supplements?What is your dog or cat eating?Have you noticed symptoms other than scratching or hair loss?Are there other pets in your home and, if so, are they experiencing similar problems?Are family members noticing any abnormal skin lesions?
Your pet will have a physical examination from head to toe, looking for evidence of parasites (such as fleas, ticks, and lice), skin lesions (such as red spots, scabs, sores) and overall health. The examination will include the eyes, ears, teeth and other body parts as well. This is because skin disease can sometimes be a manifestation of disease in another part of the body.
The results from the history (survey questions) and physical examination will lead your veterinarian in determining which diseases are most likely causing the hair loss and itching for your dog and cat. The results will also help in determining which diagnostic tests should be performed.
Specific Tests for Skin Disease in the Dog and Cat
If your dog or cat is suffering from skin disease and has been losing hair or scratching, there are several tests your veterinarian may recommend performing. This includes:
Skin scrapings to look for evidence of the mites that cause mangeSkin cytology looking for evidence of yeast and bacterial infections in the skinFungal cultures that check for ringworm and other fungal infectionsSkin biopsies if skin cancer or other serious skin disease is suspected
In some cases, if your veterinarian suspects that a more systemic disease is causing your dog or cat's skin disease, a blood screen may be recommended:
A blood screen usually consists of a complete blood count (CBC) and a chemistry profile.The complete blood count looks closely at the red blood cells and white blood cells.The blood chemistry profile allows evaluation of kidney function, liver enzymes, protein levels, and electrolyte levels.In dogs with skin disease, blood screening may also include tests that evaluate the thyroid function, including total t4, free t4, and/or thyroid stimulating hormone (TSH).
Diagnosing Canine and Feline Skin Disease with Flea Control
If your dog or cat is scratching and losing hair, one of the first things your veterinarian will likely recommend is a reliable form of flea control if you are not already using flea control. This is because fleas can be notoriously difficult to find on dogs and cats, even if fleas are the cause of the allergy. And if fleas are not the cause of the initial skin irritation, controlling fleas is still important because fleas are likely to make the original skin problem much worse.
Diagnosing Skin Disease in the Dog or Cat Caused by Food Allergy
If fleas have been treated and ruled out as the cause of the itching, your veterinarian may recommend doing a food trial. A food trial involves feeding your dog or cat a diet containing a protein and a carbohydrate source that he has never eaten before.
Allergy Testing and Immunotherapy (Hyposensitization)
If other causes of hair loss and scratching have been ruled out and your veterinarian is relatively certain that your dog or cat is suffering from atopy (an allergy to something in your pet's environment), allergy testing may be recommended.
Allergy testing can determine which substances your dog or cat is allergic to and allow immunotherapy, also called hyposensitization. This involves injecting a solution of the allergen (the substance causing the allergy) on a regular basis into your pet in an attempt to train your pet's body not to respond abnormally to the allergen."
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