Massengas, it might be because of dilatation of the veins. Cold water causes the veins to constrict and when you the get out of the bath, the veins will dilate more than usual and cause the redness. It might also be that you’re allergic to temperature extremes and this is the cause of the redness and itching (less likely cause, but definitely possible). Let me know if you have more questions. Good luck.