If a dog eats a few apple seeds, they won't cause it any harm. Apple seeds contain a form of cyanide that is poisonous only if ingested in high doses. If a couple of seeds are swallowed, the body will naturally detoxify itself, according to DogSupplies.com.

The amygdlin, a form of cyanide, in an apple seed is found in the seed covering. If the seed covering is not broken when ingested or through the digestion period the dog will not be exposed to the cyanide, notes DogSupplies.com. For best results, remove the stem, core, and seeds before feeding your dog an apple.

Apples themselves aren't harmful to dogs and actually have a few health benefits, according to Vetinfo. They are low in sodium and high in vitamin C and dietary fiber. An apple also contains omega-3 and omega-6 fatty acids, which help contribute to a dog's healthy skin and coat. In dogs with arthritis or kidney disease, the omega-6 can cause inflammation in high doses, so owners are advised to use caution when feeding their dogs apples if they are getting omega-6 from other sources. Even in a healthy dog portions should be kept reasonable, as apples can cause an upset stomach or diarrhea.