Reprinted from WOOFipedia by the American Kennel Club
Yes, dogs can eat apples. And most love 'em, too.
Apples are a great source of vitamin c, fiber, calcium, and phosphorus, and they’re a safe way to satisfy your pet’s sweet tooth (as opposed to chocolate and other doggy diet no-nos).
Two caveats: Do not feed the seeds to your dog as they contain cyanide, a toxic substance. (Some also advise keeping the stem from your pet, too.) Also, like in people, eating too many apples can cause a dog to have a bellyache and diarrhea, so serve them in moderation.