The dermatologists harp on this, and for good reason. When a dog has a skin problem, you frequently see a very non-specific outward appearance. If he's been scratching it, it just looks like it's been scratched a lot. You will probably see hair loss, flaking skin, redness, crusts, scabs, maybe some pimples. This will be the case whether he has allergies, skin infections (bacterial, yeast,or deep fungal), mange mites, or some combination of the above. You might also see this with auto-immune diseases, where the body's own defenses go haywire and attack the skin. The rule is, every skin case gets a skin scraping exam. If it's not getting better, do the skin scraping again, even if you didn't find anything last time. There have been numerous occasions when I did the skin scraping as a formality ("because you're supposed to") and found mites that I had not suspected at all.
"Ellie May" is a Collie with demodex mites(I'll get her picture on here when she comes back for the recheck; we were a little pressed for time today, as we spent a lot of time getting a year's worth of history, and then explaining the treatment plan). She has been having skin problems for about a year (and she's about two years old). Roughly a third of her body is covered with scabs, and she (along with her owners) has been miserable for quite a while.
She started out with small spots of hair loss and itching and skin damage. This was diagnosed as a "hot-spot" by her previous veterinarian. [Hot-Spot, termed "pyotraumatic dermatitis" by the dermatologists: an area of skin that rapidly develops hair loss and is red and oozing; caused by excessive scratching in susceptible individuals; only a small percentage of scratching dogs develop this type of lesion.] I suspect that they may have performed a skin scraping when Ellie May first began to have problems, but they haven't done one in a long time.
Over the past year, she has been treated repeatedly with high doses of cortisone, topical powders, and occasional systemic antibiotics (for a week, at most). In this year, she has progressed from a recurring small spot here and there, to a third of her body severely affected. She looks a lot like the dog in this diagram from the Hill's Atlas of Veterinary Clinical Anatomy, only a lot worse... not so happy. Pretty unhappy, in fact.
My first skin scraping yielded a ton of mites, and all life stages, from egg to grandpa. Those microscopic bugs are severely damaging her hair follicles, resulting in lots of secondary bacterial infection, which is most of why she's so miserable.
Most dogs carry a few of these mites on their skin, but compensate for it. Their body's defenses prevent the mites from multiplying very much, and you never see a problem. When an adult dog develops a widespread problem, you have to wonder what went wrong. I've sent out bloodwork to look for as many potential problems as I can, but here's what I think happened.
I think that her first veterinarian did a skin scraping and didn't find mites because her initial problem may have been related to something else. Over the last year, she has become immunosuppressed from too much cortisone. She may have had "normal doses" and it was just too much for her, or the doses might have been excessive. At any rate, her immune system got slowed down, and the mites took off.
Nobody checked for mange mites again, because she didn't have them to start with. Treatment was symptomatic and superficial and not very effective.
Today I followed the dermatologist's rule and did a skin scraping first. I did this because IT'S A RULE, and because the dog looked awful and I didn't want to miss anything, AND, since it was my first time to see her, I didn't have tunnel-vision from previous assessments (see my last post on Diabetes).
So now we're treating her skin infection pretty intensively, and NOT giving her any cortisone, and looking for any other problems and starting to treat the mange mites themselves. I'm optimistic that she will recover and lead a normal life.
I'll keep you posted.