A:Answer More specifically, per the PhoneSoap website (for PhoneSoap3): The UV light inside of PhoneSoap 3 is most effective on hard, non-porous surfaces such as phones, most phone cases, keys, credit cards, etc. UV light is less effective against fabrics and other porous materials because of the many shadows they create that may block the UV light from hitting the surface. The UV light can only kill germs on surfaces with which it comes in contact.