Poltergeist (1982)

Revealing mistake: When the chair moves across the kitchen floor, Craig T. Nelson goes to investigate it (after it has stopped moving). He goes up to the chair and flips it over. If you look closely, Craig almost hits the camera with the chair's legs. You can tell this has happened because the camera moves up very quickly and Craig looks straight at the camera crew with very big guilty eyes. This is more easily visible on the widescreen version of the film. (00:33:30)

Trivia: While filming the toy clown attacking Robbie, the clown's arms were wrapped tightly around Oliver's neck. He immediately said he couldn't breathe but Steven Spielberg and Tobe Hooper both thought that he was ad-libbing. When Spielberg saw Oliver's face turning purple, he realised that he really was being asphyxiated and ran over to remove the arms from his neck.

Question: What exactly is the red slime on the body of Carol Anne and her mother after they are rescued from the another dimension?