A microdermabrasion hand piece includes an elongated body portion having a particle supply channel and a waste removal channel extending lengthwise, parallel to a longitudinal axis, through the body portion; a removable tip attachable to a proximal end of the body portion, the removable tip defining a treatment orifice; the particle supply channel being oriented to direct a stream of abrasive particles, which are drawn into and guided through the particle supply channel, substantially toward a center of the treatment orifice; and an automatic vacuum relief valve assembly oriented centrally in the hand piece and generally parallel to the longitudinal axis of the hand piece, the vacuum relief valve assembly being responsive to skin contact, wherein the hand piece provides automatic limitation on skin extension, wherein extension of the skin in the treatment orifice, beyond a predetermined limit, is prevented and excessive extension of skin of various thicknesses is eliminated.