Porosity control is just that, a product to help with the porosity of your hair. Porous hair is more fragile, tends to break easily, and can be somewhat weak. PC helps to close and seal the cuticle which aides in retaining moisture and strength. It also helps to balance the ph of the hair after a chemical service such as relaxing or coloring. I am a relaxed, 3c, fine strand hair and I use PC after every shampoo because I have a demi color. Several relaxed ladies use it and you can probably do a search on it to find threads. If you don't want to spend the $ for it though, ACV works just as well (IMO).