Any diaper rash cream will take care of it. Along with any other issues ya get going on after a long session . "Triple Paste" is the best hands down, but A&D or anything else will work with a little more time.
I get neck rash from my back zip suit, to prevent it in the future get this stuff called Body Glide I havent had a rash since I started using it. Its made for runners I think I got it at ****s for like $10.
If you just use vasaline on the back of your neck you wont have that problem... I have a pretty thick neck and a big back for my size and I have to use it on my wings and neck so i dont get rashes from paddling ... it works its just annoying to bring it with you
dont ever use vaseline in conjunction with a neoprene wetsuit. Best thing you can do is somehow smooth out the thing causing the abrasion, ie duct tape. even better use seam tape. I have a flatstitch 3/2 that gives me a soreness on my neck - I just have a piece of tape over the section. My blindstitched suits do not give me a rash, so consider spending more money on a better suit next time.
I second the Body Glide which sounds "mulit-purpose" but comes in a stick and is made for tri-atheletes. Works great for your neck and safe for neoprene. I use it all of the time that i wear a suit and no more rash.