leg rash

hi
yesterday i had a 5 hour session
and got more rash on the back of my legs, since the session was son long
little red dots that hitch like a mo$%ยทยทยท"""&
what can i wear under my boardshorts to prevent it??? i've head of vaseline and tried it. but it gets real slippery while in the water
the long bicycle shorts that cyclist wear work under the boardshorts???
or only the licra surf shorts??
thanks
yesterday i had a 5 hour session
and got more rash on the back of my legs, since the session was son long
little red dots that hitch like a mo$%ยทยทยท"""&
what can i wear under my boardshorts to prevent it??? i've head of vaseline and tried it. but it gets real slippery while in the water
the long bicycle shorts that cyclist wear work under the boardshorts???
or only the licra surf shorts??
thanks