Many chemical beauty advocates say that plastic beads are gentler to the skin because they do not have harsh edges like ground nutshells, pumice, or apricot or peach kernels. They say that polyethylene and polyurethane beads are round and smooth, they roll over the skin, producing less damage to sensitive and acne-prone skin. Secondly, since they are chemically inert and have high melting point, plastic beads are less prone to oxidizing damage and will not be dislodged by detergents or acids in the scrub, because many scrubs contain glycolic or salicylic acids to speed up dead skin cells removal. Read more of this post