There has not been any reported toxicities associated with grape seed extract in dogs. It is believed that the toxin in grapes is not linked to the seed. The evidence for this is that dog's have been poisoned after ingesting seedless grapes. Though it might be best to limit the amount until scientists have discovered the grape ingredient that is the source of the toxicity.
An ounce of grape seed extract is a very high dose unless your dog is a Mastiff. That high amount can cause blood thinning, due to the anti-coagulating effect.
I suggest using a combination of Omega 3 Fatty Acids such as Flax Seed Oil, Fish Oil, and Grape seed extract. The benefit of Omega 3 Fatty acids is achieved at a total of 1000mg twice daily (of all Omega 3 Fatty acid sources) for a 80 pound dog.
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