Hissing is never dangerous. Even if your lizard does hiss aggressively, he will only attack if he feels like he has absolutely no other choice. He will most likely hiss at you before he bites. You can tell that he is going to bite by the way that he holds his head. His mouth will be open, and his teeth will be showing. You can also see the muscles on his neck tense up. If you want to protect yourself, you should stand very still so that you don’t provoke him into biting you.