The Deflating Draught is a potion which causes anything swollen by magical means to shrink back to normal size. This is the opposite to a Swelling Solution and acts as an antidote to it. It was used by Severus Snape in 1992 to deflate people who had been hit by Goyle's potion, which had exploded out of its cauldron due to Harry Potter throwing a Filibuster firework into it.