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. This is common in water sports (surfing for example), which is why you see supplemental rash guard shirts, vests, pants to minimize this occurance. Lycras work well for this as well under diving wetsuits.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?
I personally am a naturist...I prefer to be free from any cumbersome clothing under anything I wear!!
Just a males perspective....LOL...