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“Models in medi spas, which cover the whole face, are effective, and usually the treatment takes half an hour, making them good add-ons with a facial,” says Gabriel Chiu, M.D., a Beverly Hills-based plastic and reconstructive surgeon. That said, even light therapy treatments administered by pros don’t offer instant results, notes New York-based dermatologist Joshua Zeichner, M.D.: “It takes several weeks of continuous use to achieve skin improvements with light-based treatments.” Both doctors stress that LED masks for at-home use are typically less powerful, and, therefore, less effective than what you might get in an office. “For LED light therapy to work, it has to be applied for at least half an hour over any area,” says Dr. Chiu. The catch? Many of the at-home devices are made to be used just 10 minutes at a time.