Rubbery products having a transition temperature that shrink from a second shape and size toward their original shape and size upon application of energy equivalent in result to raising the temperature of the rubbery product above the transition temperature. Also, hypo-allergenic rubbery products made from polybutadiene and its copolymers, trans-1,4-polybutadiene and its copolymers, synthetic isoprene and its copolymers, or synthetic cis-1,4-polyisoprene and its copolymers. Such rubbery products (not all of which need to be made to shrink) can be used in condoms, gloves, catheters, baby-bottle nipples, and dental dams, to name just a few.