How Veterinary Dermatology Cases Are Worked Up

In an ongoing series on how different kinds of cases are worked up, today we will look at pet dermatology patients.

Dermatology, the study of skin and its diseases, is one of the most challenging areas of practice.

And I love it. Why? Simple: it is so rewarding.

Most dermatology patients arrive with a complaint of scratching. Pet owners often think that scratching equals fleas, but if you could see the size of my dermatology text book you’d know there are a lot more causes of scratching besides fleas.

Our basic list of questions for the pet lover to answer before the examination (this is called “taking the history” and history can make or break a dermatologic diagnosis):

1. How long has he had the problem?
2. Is he scratching?
3. Does he scratch more in one area than another (we almost always get the same answer to this question, and it’s, “No, it’s all over.” Rarely, in fact, is the scratching truly “all over” I say that only to prompt you to be observant before your pet goes into the doctor’s office so that you can give the all-important correct answer?
4. Does he have hair loss, and if so, is it more in one area than another?
5. Is the hair loss symmetrical (equal on both sides of the body)?
6. Does he have lesions (sores) in the skin? If so, where are they located?
7. In what area was the first hair loss?
8. Are you seeing fleas or any other insects on your pet?
9. Does he have an odor?
10. Has he had ear itchiness or drainage since this episode started?
11. Has he been treated for this before? If yes, what was the diagnosis?
12. What medications and/or shampoos are you using now and did you bring those with you as we asked on the phone?

Once we know whether the patient is itchy or not we have a road map to tell us which way we’re going. Some conditions are always itchy, some are never itchy, and some can go either way.

For the itchy patient, we’re going to look for the obvious first. Fleas, of course, but often we find no fleas on the pet but do find evidence they’ve been there. Flea BM, digested blood that fleas have eaten, dries black on the skin and hair. When we brush it off onto the examination table and spray it with water it turns red again,
because it’s blood! You can’t have digested blood without a flea to suck it out and digest it.

Allergy patients are usually itchy, too, so that’s a good thing to check for at this time.

For the non-itchy patient with hair loss and/or lesions in the skin we may be thinking of parasitic diseases in which the parasites are inside the skin, or autoimmune conditions that cause the immune system to attack the skin.

So, what’s rewarding about a discipline that can be so frustrating and difficult?

1. Most dermatologic problems eventually have a diagnosis and a treatment.
2. When the pet’s condition begins to respond to treatment the pet, his owner and his doctor are all happy.
3. Seeing a full coat of healthy hair on a previously-bald dog or cat? Priceless.
   See you tomorrow, Dr. Randolph.