The Robo itch is intense and painful itching/rash caused by taking recreational doses of Robitussin Cold and Cough medicine. Does not happen to everyone, but if it happens to you, you can sometimes avoid it by taking an antihistamine, such as benadryl. Watch out for syrups containing antihistamines though!
Me: Man, the last time I did DXM I got the worst robo itch. I was in so much pain I thought I was on fire. I was so close to scratching myself raw that I decided that it would be my last experience with robo.