They say laughter is the best medicine. Unless, that is, you feel like you’re being tickled to death — or at least to the point where you're about to wet your pants. Yet tickling isn't always a negative experience. Consider parents who tickle their newborns to elicit sweet baby giggles or lovers who tickle for flirting and foreplay. Some people even make appointments to be tickled, at the CosquilleArte Spa in Madrid — the world’s first tickle spa, where therapists use their fingertips and soft feathers to soothe their clients into relaxation.

Whether tickling makes you giggle or cringe, we dare you to read the following fascinating facts about tickling without cracking a smile — or feeling a little tingly.