How to Avoid the Five Most Common Mistakes in Dermatology
Lori A. Thompson, DVM, Diplomate ACVD
Animal Dermatology Clinic
Pitfall #5: Failure to Obtain a Complete History
In veterinary medicine, history often plays an essential role in helping us formulate a list of
differential diagnoses. Obtaining a thorough history is CRITICAL in veterinary dermatology.
The history truly is one of the most important parts of the dermatologic examination. You don’t
have time? Use dermatologic history forms. Several are available from various sources such
as AAHA, VIN, and your colleagues. Train your technician to get some of the information for
you! Your technician can be a valuable asset in giving you a “heads up” before you even enter
the room (hey doc, the dog in room 4 is scratching like mad and so is the owner).
By having clients fill out a history form or training your technician to ask some of these
questions before you enter the room, it allows you to be more focused with additional follow up
questions. Clients can provide you with important clues and help you narrow down the list of
differentials, but you need to ask and listen.
Sample questions:
 When did the itching start?
 Did it start suddenly or was it more gradual?
 How old was Woofie when he started chewing the pads of his feet off?
 Are any other animals in the house affected?
 How about people in the house?
 Are the clinical signs seasonal or non-seasonal?
 Have the clinical signs changed or are they the same as when they started?
 How about the environment? (indoor only, outdoor in a kennel environment, hunting?)
 Has the environment at home changed (New baby? New dog? New kitten?)
Pitfall #4: Histopathology – Performing it too Late in the Course of the Disease
Practitioners are often frustrated with inconclusive results (“superficial perivascular dermatitis”).
Histopathology is your friend and can be invaluable in making a diagnosis, BUT, you have to
learn to biopsy sooner versus later, AND, find yourself a dermatohistopathologist to send your
skin samples to.
Key points:
 Know when to biopsy
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Know the proper technique (don’t prep the sample or roto-rooter through the skin with
the punch biopsy)
Pick a dermatohistopathologist and develop a relationship with them. Send them a
good history. Many dermatohistopathologists appreciate digital images. In today’s age
of technology, it’s not hard to shoot an email and attach a few digital images.
Site selection is very important
o Pustules for pemphigus
o Early depigmentation for DLE (not an ulcer)
o Avoid old, chronic lesions
Sooner rather than later!!!
Pitfall #3: Appropriate Antibiotic Usage
This is a lecture in and of itself! In the past, dermatology = cephalosporins. That past was not
too long ago. Now, with the advent of many of the MRSA, MRSI, MRSP infections and all of
the social awareness this has created, choosing the appropriate antibiotic, the proper dose,
and adequate resolution is even more critical than it has ever been before.
The question of whether to select an antibiotic empirically or perform a culture and sensitivity is
a tough one. Cytology (refer to pitfall #2) can guide us in making these types of decisions.
When is a good time to culture? Well, if you’re seeing organisms other than cocci on cytology,
unusual lesions, persistent or recurrent infections, concern about methicillin resistant
Staph…these are all indicators to think about submitting a culture. In the case of otitis, the
presence of rod bacteria on cytology should be a trigger to reach for that culturette.
So, what is the best way to take a sample for culture of the skin? Talk with the laboratory you
use. They may prefer a culturette swab sample, or they may prefer a biopsy punch of the skin
submitted in a red top tube with sterile saline. Do what they suggest to maximize your chance
of obtaining an appropriate diagnosis. Remember, this is NOT a skin biopsy…so you need to
PREP the skin first this time and use sterile technique.
Sometimes you will obtain multiple isolates. When in doubt, it is best to choose your antibiotic
based on Staph pseudintermedius sensitivity, but combination therapy is occasionally
necessary. Duration of treatment is critical. Treat for a MINIMUM of 3 weeks. Deep
pyodermas may require 8-12 weeks of antibiotic therapy. Education your owners so they know
what to expect.
Pitfall #2: Not Obtaining Good Skin Scrapings and/or Cytology Samples
Every derm patient gets cytology, skin scrapings, and a parasite treatment trial (see Pitfall #1).
Every one! Not only is this good for your clinic financially, but these are not difficult to do and
will help you narrow your differential list considerably.
Skin scrapings:
 What parasite are you looking for? This makes a difference as to where you scrape and
how you scrape.
 Superficial scrapes = Scabies
 Deep scrapes = Demodex
 Examine the slides under low power, lower the condenser on the microscope for the
best viewing
 Demodex – count mites per low power field, distinguish eggs, larva, nymphs, and adults
along with live versus dead (important for follow up monitoring)
 Negative skin scrapings do NOT rule out scabies.
Cytology – bacteria and yeast are a major cause of pruritus. These organisms can easily
complicate the diagnosis of allergic disease. Secondary infections may also be the primary
cause of pruritus in patients with diseases typically thought of as non-pruritic (hypothyroidism,
demodicosis, hyperadrenocorticism).
 Slide preps
 Acetate tape preps
Pitfall #1: Forgetting the Power of the Flea
Flea allergic dermatitis is the most common skin disease seen in general small animal practice
in most countries of the world. Despite modern advances in flea control, flea allergic dermatitis
is still routinely seen in a dermatology specialty practice. Why is this when newer products are
more effective and when the majority of small animal practitioners are very aware of flea
allergic dermatitis in dogs and cats? Not surprisingly, convincing the owner that you are
making the correct diagnosis is one of the most difficult tasks when you suspect flea allergy.
The majority of flea product failures are due to poor compliance. When a flea product “fails”,
the pet owner views this as the development of resistance. Common responses to the
question, “How often do you use flea control?” range from:
 Never! Fifi never goes outside.
 Monthly “during warm weather”
 Every 6 weeks (that’s what the box says!)
 My wife/husband/son/daughter takes care of that
 The flea stuff is what caused THIS in the first place, so we stopped it!
Failures in the management of flea allergic dermatitis strongly correlate with owner disbelief
that fleas are the problem. This can be due to the fact that the owner never sees the fleas,
cultural biases against having ectoparasites (it’s considered “dirty”), etc. When in reality, the
most common causes of treatment failure are some or all of the following:
 Failure to treat all in contact animals (this includes indoor/outdoor cats, visitors)
 Failure to use the flea product properly (dividing the large tube between 3 Chihuahuas)
 Failure to maintain consistency in treatment
 Failure to deal with environmental issues (especially in severe cases)
 Substitution of prescription products with less expensive, less effective, and less safe
“spot-on” products from pet stores, Costco, Target, etc.
So what can we do? Owner education is critical. Get them to “buy in” to your diagnosis before
you tell them what the diagnosis is! Ask questions such as, “Does Snuggles itch more on the
front half of his body or the back half of his body?” Discuss the three most common allergic
skin diseases in dogs (atopic dermatitis, food allergic dermatitis, and flea allergic dermatitis).
Talk about the distribution pattern of the lesions for the above three diseases and let them
begin to draw their own conclusions. If possible, explain how there could have been a reason
for treatment failure in their previous flea control methods. And then last but not least, diffuse
the cultural bias for ectoparasites by making it acceptable for their pet to have fleas. For
example, in Indiana I talk about how rough the flea season is and how I now treat my pets year
round or they acquire fleas. Discuss how important it is to rule out the most common of the
allergic skin diseases before progressing to further expensive and time consuming tests.
This is where history plays a role yet again. It is important to tailor your client’s flea control
program to their individual life style. Do you have a client that is afraid of using topical
“pesticides”? Well, maybe an oral flea prevention is better for them. Consider having a
handout that you can send home with them that describes the various flea products you offer
and why YOU have chosen to carry those particular products. They trust you and want to
know what you think!