When being tickled most people start laughing but this is the body actually experiencing panic and anxiety. The feeling, although initially perceived as enjoyable, is a lot similar to having a tarantula crawl on your leg. The sensation is considered a defense mechanism if something hazardous such a poisonous insect, for example, gets dangerously close to you. The body must have a prompt reaction to this unexpected touch and, since there is no time for anything else, brings forth the panic reaction. It’s even more interesting that when you are being tickled by someone that you don’t want tickling you, the sensation is more like an actual panic reaction rather than just laughter.