Canine atopic dermatitis (AD) is a common allergic skin disease of dogs that requires life-long treatment with a variety of methods. The benefit of essential fatty acid supplementation has been known for several decades. Most recently, use of essential fatty acid-enriched diets has become common. In this study, 20 dogs with year-round AD were enrolled in a randomized, single-blind, crossover study to determine the benefit of a commercial diet (Eukanuba Veterinary Diet Dog Dermatosis FP Formula) with a home-cooked, equivalent fish and potato (control) diet. Dogs were fed 1 diet for 4 weeks and immediately thereafter fed the second diet. Owners completed a visual analog pruritus scale. Owners could not be blinded due to the nature of the diet, but the investigators were blinded and examined dogs on days 0, 30, and 60 and scored the dogs using the Canine Atopic Dermatitis Extent and Severity Index (CADESI). Sixteen dogs (8 in each group) completed the study. Dogs in group A were fed the test diet followed by the home-cooked diet. Dogs in group B were fed a home-cooked diet followed by the test diet. CADESI scores significantly decreased in dogs fed the test diet and increased or remained unchanged when they were fed the home-cooked diet. CADESI scores decreased in 15 of the 16 dogs but by less than 50%. Pruritus scores decreased in 11 of 16 dogs fed the test diet, but in only 2 of the 11 dogs did the owners report a decrease greater than 50%. Study supported in part by Procter and Gamble Pet Care

COMMENTARY: The obvious take-home message of this study is that there is good evidence to recommend a trial of essential fatty acid-enriched diets as an adjunct therapy for dogs with atopy. The true benefits of such diets can be maximized by ensuring that the dog is receiving regular flea control (no "ifs," "ands," or "buts"). This is an expensive disease to treat, and you don't want something as simple as fleas triggering an episode of pruritus. Second, before starting the diet trial, be sure the dog does not have a yeast or bacterial infection. If in doubt, conduct a treatment trial for 30 days. Make sure the clients are using as much of the appropriate topical therapy as they are able and willing to. Then, give the diet a "fair chance." In this study, the test time was 30 days. I usually recommend at least 2 months. Be up front with the client: tell him or her that the diet may help with the pruritus and/or it may be more helpful with the inflammatory reaction of the skin. Finally, remember that treatment trials for atopy are difficult for many reasons, and in the past "conclusions" were made on subjective data collection (ie, "all better," "somewhat better," "slightly better"). The current standard for treatment trials in veterinary dermatology involves the CADESI scoring system. Be sure to determine whether the investigators are reporting data using this scale.

Efficacy of an essential fatty acid enriched diet in managing canine atopic dermatitis: A randomized, single-blinded, cross over study. Bensignor E, Morgan DM, Nuttal T. VET DERMATOL 19:156-162, 2008.