AS WE LEARNED IN LAST MONTH’S ARTICLE, a logical, problem-based, step-by-step process is our best bet when it comes to dermatology. This requires patience, method and time; much more so than a pattern recognition approach which relies more on the practitioner’s experience. You may need to juggle your owner’s expectations, which will be more focused on immediate symptomatic and reactive modes of management. Consider the following scenario: a pruritic dog enters your veterinary practice… just the same as they did six months ago. Tracking back, you see that this patient visited in 2010, twice in 2012 and again in 2015. With three vets telling slightly different versions of the same story, you can see that little progress beyond empirical therapy and a couple of skin scrapes has occurred. The words “ectoparasites”, “allergy”, “sensitivity”, “seasonality” and “secondary infection” litter the dog’s clinical notes – and your mind. Simultaneously, bottles of antibiotics and steroids stare back at you from the pharmacy. With the best of intent you know you can (medically) press the reset button, similar to what was done previously. This pleases the owner, but confuses the diagnosis of course. It sets a repeating pattern of dependence that many chronic skin cases get caught in, and risks corticosteroid-related side-effects, concurrent (often yeast) infections or bacterial resistance. Beyond this comes the realisation that repeat flares are bound to become more frequent. Not great for keeping your client on-side. This is why a problem-based approach is essential. First-sight diagnoses are quite dangerous in dermatology for a number of reasons, not least because we’re dealing with the body’s largest organ – comprising 12% of the body weight of the adult dog3 and therefore the consequences of ill health are great. Let’s appreciate that among the thousands of diagnoses and origins of skin disease, this organ can only react in a relatively limited number of ways. Technically, a significant differential diagnosis list should accompany every problem recognised in our case, from which our systematic work-up can be drawn. One differential is cutaneous adverse food reaction (cAFR), often used interchangeably with the terms dietary allergy or food hypersensitivity. Most commonly, dogs present with signs indistinguishable from canine atopic dermatitis. As is the trend in humans, it is suspected that there is a higher prevalence in younger animals, with puppies more often diagnosed than adult dogs.5 Simply put, diagnosing cAFR requires identifying the offending dietary allergen (or allergens), removing it, and then putting it back in the bowl. Taking the patient’s complete dietary history and ensuring no previously fed ingredients are in the test diet is one approach to finding the “right” elimination diet. The second approach involves providing the patient with a diet which is as “unrecognisable” to the immune system as possible, and therefore unlikely to trigger a hypersensitivity reaction. This of course is the intention of hydrolysed diets. It’s worth reminding clients that elimination diet trials are indeed a diagnostic test. Just the same as a blood test depends on the use of the correct anticoagulant or the diagnostic value of an x-ray depends on patient positioning, this trial needs to be carried out in a very precise manner to result in a worthwhile judgement. Sufficient time should be set aside to prepare for a trial and communicate guidelines thoroughly, checking all caregivers’ understanding and signposting your expectations of the process. Most cAFR dogs respond at least partially within eight weeks, but some require longer.5 Dermatology is a very logical discipline. With a sensible and systematic approach, a good dose of patience and clear communication, a definitive diagnosis and the appropriate treatment plan can be established in the majority of cases. Some may argue that a similar armoury of therapies will be used in a pattern-recognition approach, but with problem-based logic on our side, we (and pet owners) will feel much more in control of those pruritic flares. Where food is involved or is a complicating factor, finding the right diet for each sensitive individual will help bring them below the “pruritic threshold”. With monitoring revisits and a proactive and measured response from both the owner and veterinary team, the frustrations which come with dermatology cases can slowly evolve to an appreciation of the skin as a sometimes sensitive, sometimes obstinate organ. Let’s appreciate that chronic skin conditions are rarely cured, but effective, safe, affordable and convenient life-long management can often be made a reality.
References and further reading
1. Hill, P. and Olivry, T. (2001) The ACVD taskforce on atopic dermatitis (V): biology and role of inflammatory cells in cutaneous
