Some—but certainly not all—veterinary research has shown that combinations of fish oil and evening primrose or borage oil can relieve seborrhea, pruritis, allergic itching, scurf, and other canine coat and skin disorders. Oils that provide EPA or combinations of EPA, DHA, and GLA are needed to show significant improvements of these conditions. [1] Vegetable oils such as olive, sesame and soybean are so ineffective for these conditions that they are used as placebos.

A recent study found flax and sunflower oil to be equally effective but short-lived in improving the condition of skin and hair coat in normal dogs. The authors posited that LA, not LNA and its downstream products, may have explained the observed equal improvement. Many dog owners supplement their dogs' diets with fats. Is the LNA-rich oil necessary or superior? In this study it was not. [2 ]

Humans, dogs and cats can all suffer from atopic dermatitis. For all three, the characteristic allergic skin irritation, itching, and inflammation are related to food and environmental allergies as well as PUFA metabolism; therefore, a multidimensional treatment plan is needed.

In an open, unblinded, uncontrolled study at Cornell University, a hypoallergenic lamb and rice diet (IAMS) was fed to 18 atopic dogs with pruritis and multiple diagnosed allergies. The special diet also controlled n-6 to n-3 PUFAs at 5.5:1, about four times lower than their normal diet. Eight dogs responded to the diet, and pruritis was controlled within 7 to 21 days. Symptoms returned 3 to 14 days after they were taken off the special diet but abated again when the diet was reinstated for six weeks. [3] Granted, the success rate was less than half, but it was due solely to dietary changes. If the researchers had added fish oil and perhaps some other supplements and run the trial for six months, results might have been even better.

In a controlled study of 16 dogs with pruritis, conducted at the University of Florida, Gainesville, 11 of 16 owners reported significant improvement in their dogs' coats with high-dose (1 ml/4.55 kg body weight) fish oil. Clinically, pruritis decreased 38 percent and hair loss 45 percent. [3 ]

Despite these positive studies, overall results in fish, evening primrose, or a combination of oils in clinical studies on canine and feline skin and coat conditions have been inconsistent. Such study results have been explained by (1) short study duration; (2) low oil doses; and (3) PUFAs in the regular diet not accounted for. [4 ]

Researchers have concluded that because dogs have long coats and an excellent ability to burn fat for energy, they need five to 10 times as much oil as humans to achieve measurable clinical improvement. Doses for dogs are 1­6 Tbs/day for the first six weeks or so; after improvement, one-half or one-third doses can be used. Doses should be scaled up with body weight; roughly, dogs less than 20 pounds take 1­2 Tbs/day, dogs less than 50 pounds take 2­4 Tbs/day, and dogs more than 50 pounds take 4­6 Tbs/day. Mix oil in food, or let dogs lick it directly off a spoon. Owners may wish to feed hypoallergenic dog food with the oil for pruritis, diagnosed or suspected allergies, and chronic itching. Success is likely when both issues are addressed simultaneously.
—CLB
References

1. Bond R, Lloyd D. A double-blind comparison of olive oil and a combination of evening primrose oil and fish oil in the management of canine atopy. Vet Rec 1992;131:558-60.

2. Rees CA, et al. Effects of dietary flax seed and sunflower seed supplementation on normal canine serum polyunsaturated fatty acids and skin and hair coat condition scores. Vet Dermatol 2001 Apr;12(2):111-7.

3. Scott DW, et al. Effect of an n-3/n-6 fatty acid-containing commercial lamb and rice diet on pruritus in atopic dogs: results of a single-blinded study. Can J Vet Res 1997;61:145-53.

4. Logas D, Kunkle GA. Double-blinded crossover study with marine fish oil supplementation containing high-dose eicosapentaenoic acid for the treatment of canine pruritic skin disease. Vet Dermatol 1994;5:99-104.

5. Watson TDG. Diet and skin disease in dogs and cats. J Nutr 1998;128:2783S-9S.