A couple years ago, I realized that I was constantly itchy and rash-y. My family has a history of allergies and mild skin conditions (my Dad calls it the "crud"). After some time, I figured out that it must be dermatographism—an allergy to skin pressure, essentially. Since then I've taken a Zyrtec a day and alleviates the itchiness from the chronically-unable-to-concentrate-craze-inducing level to the acute and mildly annoying. I should probably explore a real diagnosis and treatment at some point, but I very much sympathize with anyone plagued by ceaseless itching. It's pretty horrible.