Crikey, I wish I hadn't googled images of swimmer's itch! 

I don't think it's that, fortunately. Otherwise I don't think I'd ever want to get in the water again!
The rash is on the inside of the elbow joint on both arms. Little red spots, most of which have gone now. I've not noticed a rash anywhere else, just felt very itchy! I'm allergic to latex amongst other things, so know I am prone to allergy.
I didn't use anything like body glide, so it's not that. I'm sightly baffled!