When I was a kid I spent part so my summers and holidays with my best friend down in Ensenada, Mexico. When I was a teenager I took up smoking for a while. On one of my visits we ran out of American Marlboros, so we borrowed a few packs of Mexican Salems from a neighbor/friend.
It resulted in the only bout of diarrhea I ever experienced in Mexico.
You are supposed to smoke em in you lips not in your bum!