Why do the palms of your hands look all red and splotchy after you use the bathroom sometimes?

Are you sure you are not just noticing this at that time? Look at your palms at other times, when you are not as likely to, and compare. Compare them with someone else that is the same gender and general age and build. Even if it is just after you are in the bathroom, it may be the temperature of the water you are washing your hands with, or an allergy to the soap. If you are talking about an actual rash, or really red palms, you need to have a doctor check you out. There's all sorts of things that can give you rashes.