Stephen Waisglass, BSc, DVM, MRCVS, CertSAD, DACVD

The skin is the largest organ of the body and, in the view of many practitioners, it often accounts for the largest number of headaches. One would expect that since the skin is so easy to visualize, a diagnosis should be an easy task when compared with other, more hidden body organs. The problem is that many skin conditions have the same clinical presentation.

Behavior and medicine (or physiology) are not mutually exclusive; there is a complex interaction between the two. Studies published recently in the British Journal of Dermatology concluded that human patients subjected to brief psychological stress (PS) developed an increase in Psoriasis Area and Severity Index (PASI) and itch 4 weeks later(Verhoeven, 2009).

Once you have finished interviewing the witnesses, the next step is to collect the evidence. A minimum database ("derm–due-diligence") for any pruritic pet should include skin scrapings, close examination for external parasites (fleas, ticks, and lice), acetate tape tests, cytology and possibly coat brushings.

In order to understand when and how to culture, it may be useful to first understand a bit about the etiology and pathophysiology regarding pyoderma:

Non-responsive or chronic and recurrent otitis externa is a common reason for pet owners to leave their regular veterinarian and seek second (and third, fourth and fifth........) opinions. Proper management of these conditions takes a co-ordinated approach that includes strong history taking skills (keeping in mind the primary, predisposing and perpetuating factors involved in otitis), a thorough physical and otoscopic evaluation, appropriate diagnostic tests and the institution of a sound therapeutic plan that addresses the underlying factors while treating the current condition.

Skin disease is the second most common reason for a pet to be presented to a family veterinarian (Hill, 2006). The most common reason is preventive care! Pruritus is the most common dermatological presenting complaint along with "I need to stop that disgusting licking noise that my dog does at night!"

Once we have ruled out the possibility of parasites and treated a secondary microbial dermatitis, our history taking skills and physical examination will often point to an allergic etiology as the cause of the pruritus. In the non-seasonal dog, rule outs will include an adverse food reaction and environmental allergy.