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: In the swimming pool scene with the mother near the end, the actress didn't know it, but those weren't fake skeletons.

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