CSU is the medical term for chronic hives that last for 6 weeks or longer where there is no obvious external trigger such as cold, heat, pressure, water, substance, exercise, and stress. It presents as a skin reaction with itchy welts that can be small or large. The welts are often skin-colored, or reddish on White skin and purplish on Black skin. CSU affects people of every age, but it is most common from age 40-60. Women experience CSU about twice as much as men.