Movie special effects usually come with a big price tag. They can be complicated, requiring specialised (and licensed) skill sets. Some are also very dangerous if not performed correctly. Blood squibs are no exception. They’re the packs that you see explode whenever somebody gets shot in a movie or TV show.
Traditionally, squibs hold a small explosive charge that detonates on demand. You’ll generally need to be licensed in order to create and use them, and there are all kinds of safety checks. There are safer options, though. Such as this one shown in this video from John Hess at Filmmaker IQ. We see us how to make our own (relatively) safe squibs using a very minimal list of ingredients..