Most ponies are sane enough to only put a single piece of candy in their mouth at a time.

My warnings were exactly because of people like Teddie. If he has too many at once, the effects won't wear off on their own. That can be dangerous, since poison joke is highly unpredictable. If something happens like him growing into a giant, or belching fire...

[Do you really want a 20-foot-tall rampaging Kyouko running through town breathing flames, Pokey.]