Q. I know chocolate is harmful to dogs. What else hurts pets but not people?

A. Dogs and cats are commonly poisoned by drugs intended for humans, and several foods are uniquely toxic to dogs, said Dr. Karyn L. Bischoff, a veterinarian and toxicologist with the New York State Animal Health Diagnostic Center at Cornell University.

Dr. Bischoff listed canine food risks including the artificial sweetener xylitol, macadamia nuts, onions, garlic, leeks and chives. Grapes and raisins sometimes pose a threat; since the consequence could be life-threatening kidney failure, she said, “why would you take the risk?”

As for chocolate, humans seem to be a little more resistant than dogs and cats to stimulants in it that are similar to caffeine, but even humans can get sick after consuming too much, Dr. Bischoff said. Baking chocolate, cocoa and dark or semisweet chocolates are the most dangerous.

Part of the problem with drugs is that cats and most dogs are relatively small, so a human dose is far too much. But Dr. Bischoff noted that some drugs, including acetaminophen in cats and ibuprofen in dogs, are toxic to pets because of their unique metabolism.

Dogs are often poisoned when they consume spilled medications, she said. Cats do so less frequently, but seem to be attracted to the antidepressant venlafaxine (Effexor), and Adderall, used to treat attention deficit hyperactivity disorder.

A more complete list of pet poisons can be found on the A.S.P.C.A. website.