l have a soft top surfboard and whenever l use it, my thighs, knees, and even the tops of my feet get really bad rashes, and the skin gets all raw and oozey and it really hurts (sorry if that was too much info) but why does that happen? And when l use a fiberglass board im totally fine? What is up with that?

l would say that u r probably not allergic to ur soft top board, only because if u were, u have noticed this type of reaction earlier, since the material is used on things other than surfboards as well.

if u have really sensitive skin, that may be the cause.

do u wear anything while u surf? rash guard? wet suit? it could be the combination of ur skin being particularly sensitive to the material & the drying characteristic of salt water. if it only happens when u use a soft top, that would be my best guess.

same thing happens when you bodyboard without a rashguard so you should get one because the combination of the material does that. fiberglass doesnt do this because your skin kinda just slips off the board
you might wanto also wax your soft top if you dont have a rash guard or wetsuit

but your not allergic to your board

Probably irritation from rubbing against the board although there may be a slim chance that you are sensitive to the material that is made out of. Wear a rash guard. You could also try to find one of those lotions that creates a protective layer, although
i am not sure how long they would hold up in water.

It could be a couple of different things.

Most likely scenario is it is friction between ur skin & the board. Less friction on a glass board. Get a rash guard (or a wet suit) & see if that fixes things.

Soft tops can hold water, which means they can also hold all the crap that is in the water. If you've been surfing in an area with drainage run-off, u may have some bacteria trapped in the material of ur board. That could be causing more skin irritation. Like l said, though, it is more likely just friction.

You could trying to wax ur board too. In theory that is supposed to create more friction, but in this case it will be good. The most likely problem is there is friction enough to catch at ur skin, but not enough to hold u in place, which is why you're getting rashed up. The wax will keep u put, so there will be less sliding around on ur board, therefore less friction.