Goosebumps - Monster Blood IV

the long version

"Evan Ross can't forget about Monster Blood - the evil green slime that never stops growing. It can turn ordinary pets into ferocious animals and twelve-year-old kids into freakish giants. But now there's a new kind of Monster Blood in town. It comes in a can just like the others. Only different is this slime is blue instead of green. And instead of just growing, it's multiplying - into terrifying blue creatures with razor-sharp teeth..." (from the book's blurb)