"Spit out your cherry seeds because they contain the poisonous compound hydrogen cyanide," Dr. Kantor said.
That goes for other stone fruits like peaches, plums, and apricots. But don't worry about it too much. Hydrogen cyanide is a poison, yes, but you'd have to eat a ton of cherry seeds before it would kill you. The limit for a 150-pound human is 703 milligrams of hydrogen cyanide per day, according to the National Institute of Health, which is safely hundreds of cherry seeds.