Fish oil is good for dogs – and cats! Veterinarians first used omega-3 fatty acids in the form of fish oil to treat canine allergies but now recommend it for a wide variety of conditions ranging from kidney disease to arthritis and high cholesterol. Adding fish oil to your dog's food provides anti-inflammatory effects and can help relieve itching due to atopic dermatitis, an allergy-related skin condition.
You can get fish oil supplements designed for companion animals from both Nordic Naturals and Animal Essentials (and, I'm sure, from other sources), but you also can use fish oil meant for humans as long as you choose the correct dosage. For example, Nordic Naturals recommends one capsule of its 1500 mg soft gel fish oil for large dogs weighing 20 pounds or more. Smaller animals should get smaller doses. If you use fish oil that is intended for humans, you can give larger dogs a capsule or two (depending on the dosage) and puncture a capsule to squeeze some of the contents into the food of smaller dogs or cats.
(To reduce my risk of heart disease and cancer I take two grams of fish oil a day and also eat fish – usually sockeye salmon – two or three times a week. I recommend that everyone eat two or three servings of fish per week, take a daily fish oil supplement or consume another source of omega-3 fatty acids.)
Before dosing your dog or cat with fish oil meant for humans or pets, I suggest consulting your vet, particularly with regard to dosage. Pets with allergies may need higher than the standard dosages, and they also may need supplemental GLA, an omega-6 fatty acid that improves skin health. Your vet can best advise you about dosages and whether or not a combination of the two would work better for your pooch than fish oil alone. You may not notice changes for at least six to eight weeks, so be patient.
My dogs do not have allergies or skin problems, but I add fish oil to their food at every meal for general health maintenance.
Andrew Weil, M.D.