Deodorant is a $75 billion global industry. Culturally, sweating can be considered as shameful, but its physiological purpose is what distinguishes humans from most mammals. In her quest to examine the science of sweat, journalist Sarah Everts visited sensory analysts who bunny sniffed her armpits, discovered chromhidrosis (sweating in colors), and uncovered why sweat, like tears, is salty. Her book is “The Joy of Sweat.”