Makeup, exfoliation, hydration, or masking are no longer women’s work, so to speak. Male grooming has undergone a dramatic change over the past several years to become one of beauty’s most dynamic segments, reaching $4.5 billion  in 2016, according to Kline’s latest study covering the US male grooming market. “The taboos are slowly dropping, and a growing number of men are using anti-aging serums and masks, beauty devices, and even makeup,” said Naira Aslanian, the report’s manager. “W...