A randomized, double‐blinded, placebo‐ controlled multicenter study on the efficacy of a diet with high levels of eicosapentaenoic acid and gamma‐linolenic acid in the control of canine atopic dermatitis

Abstract

The purpose of this study was to evaluate the efficacy of a diet with high levels of eicosapentaenoic acid (EPA) (480 mg/megajoule) and gamma‐linolenic acid (GLA) (50 mg/megajoule) in the control of clinical signs in dogs with atopic dermatitis. Selection of dogs with atopic dermatitis occurred according to a strict protocol; dogs with ectoparasites, endoparasites, dermatophytosis, Malassezia infection, active flea allergy dermatitis, hypothyroidism or food allergy were excluded, as well as dogs currently treated with hyposensitization, glucocorticoids, antihistamines, NSAIDs and dietary fatty acid supplements. Dogs were only selected if they met the diagnostic criteria for atopy and when atopy was confirmed by a positive intradermal test correlating with the history and clinical signs. During the entire study, flea control was applied and secondary pyoderma or Malassezia infections were controlled with antibiotics or topically applied lotions. The owners were informed that the diet and/or capsules might be treatment or placebo. The dogs received either a treatment with the test diet plus a daily placebo capsule, or the dog's usual diet plus a daily placebo capsule for a period of 10 weeks. The treatment diet provided 240 mg EPA/kg metabolic weight and 25 mg GLA/kg metabolic weight. Owners who judged that the treatment during the study had not been effective could participate in a double‐blinded crossover period during which the dog received another treatment. At the start and end of the study, the severity of the following clinical signs was scored: pruritus, shedding, scaling, dry skin, erythema, smell of coat and alopecia. In total, 13 dogs received the control treatment and 15 dogs the test diet. Of the 13 control dogs, nine followed a crossover period on the test diet, which brought the total number of dogs on the diet to 24. The score after 10 weeks of treatment was expressed as percentage of the score at week 0. After 10 weeks of treatment, scores for intensity, frequency and total score for pruritus in dogs fed the test diet were significantly lower than scores for the control dogs (P = 0.005, P = 0.013, P = 0.005, respectively); the average score was reduced to 67, 65 and 53% of the initial score, respectively. For dogs on the diet, the score for erythema was significantly lower than the score from the control dogs (P = 0.019) and was reduced to 66% of the initial score. Thirteen of the 24 owners of the dogs fed the test diet (54%) indicated that the skin and coat condition of their dog had improved compared to four of 13 control dogs (31%, P = 0.030). The dogs’ plasma and cutaneous fatty acid compositions changed significantly on the test diet and were similar for responders and nonresponders. From this study, it can be concluded that a diet with high levels of EPA and GLA is effective in the reduction of pruritus and erythema in dogs with atopic dermatitis, but that not all dogs respond to the diet. Funding: LEO Animal Health.