Well this is a pretty old movie, guess I saw it in 1999 so the movie would have released before that. Well the part of story which I remember is: 2 girls go to an exhibition where one of them checks out a mask and just tries it out. Then they plan to go for a movie, the girl who tried the mask suddenly starts bleeding from her face and then she rushes up to the toilet. Then it increases badly, she the becomes a devil! She starts biting all and it spreads, then others start fighting them for survival...
well that's the short description I remember.. Anyone with good mnovie knowledge or who has watched it can send me the movie name to my email id >Removed< so that I can get it...

Demons (http://www.imdb.com/title/tt0089013/)