Chafing rashes can occur even if you don't have allergies. Anytime you have water sitting next to your skin and material moving for longer periods of time you can get chafing rashes.Is this "rash" you write of similar to the allergies finGrabber mentions below? I've never worn neoprene so I don't know if I'm allergic to it but I do have very sensitive skin. Is a neoprene allergy quite common?
Ah, yes... chafing. Sadly, I know it well!