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Follow your nose

The saying is usually love at first sight, but your nose plays a part too. Pheromones, which are chemical messengers, are theorized—but not proven—to play a part in human sexual attraction. (They're major players in insect behavior.)

Fisher says she isn’t a fan of the pheromone theory, but believes smell is a part of love.

“Once you fall for someone, their smell can be a powerful thing,” says Fisher. “Women will wear their boyfriends T-shirts and throughout tales in history men have held on to their lover’s handkerchief.”