If the manufacturer soaks the sponge in some booster chemical, and then puts it in the package it is legal for you to use it. If you buy the same booster chemical and put it on the sponge, it is illegal, even if all you are doing is restoring a factory boosted rubber to its original condition.. Nobody seems to be able to justify this but that is the rule all the same. Originally Adham Sharara said the ban on boosters was a safety and health issue, but of course, one of the main ingredients is the same as baby oil -- something we rub onto the skin of babies.