Extreme temperatures are being touted as the latest ticket to tighter skin from head to toe. New professional in-office treatments use high levels of heat (via radio frequency or laser, like WarmSculpting with SculpSure) or cold (with technology like cryolipolysis, also called CoolSculpting) to injure fat cells, which then die and are absorbed or expelled by the body, says Dianne Quibell, M.D., a cosmetic laser surgeon in Wellesley, MA. “Cold treatments cause blood vessels to narrow and the superficial muscles in skin to contract, which then reduces puffiness and temporarily tightens skin,” says Paul Jarrod Frank, M.D., a dermatologist in New York City. “Heat treatments have been shown to have long-term skin-firming effects.” On average, the procedures (which can cause mild discomfort and minor side effects, like bruising and soreness)…