Kids sleepwear is supposed to be made of material treated with a chemical to make it safer for kids in event of a fire. That way, if there is a fire, they have a better opportunity of surviving and not being burned as the clothes catch fire. Alternatively, kids can wear snug fitting pajamas, which are not required to be treated. Since the kids will not be wearing the pillowcase to sleep in, the "pajama safe" standard does not apply.