Need some info about real life circumstances of this trope. Side effect of rabies.
It can also be used to show cyanide poisoning but this is a case of Didnt Do The Research
See also Fake Rabies
, where someone with soap or cream in their mouth is mistaken for this and Phlegmings
- On the SpongeBob SquarePants episode "SpongeBob, Sandy and the Worm", Mr. Krabs foams at the mouth at the thought of having to pay Sandy for capturing the Alaskan Bullworm. "I'd rather have that worm come in here and eat you all alive!" Cue the awkward looks.