Did you follow an elimination diet to find out what you were sensitive to, or was it obvious? I'm considering an elimination diet but everything I read about a diet plan are different.
I started when I was 32. Get a big board to start with. Know that it's probably 95% paddling and 5% actual surfing. The advice to bodyboard or even body surf with fins is a good one. I'm teaching my son to body surf/body board first, then move to surfboards when he's old enough. It looks much easier than it is but if you stick to it, it is very rewarding. Go every chance you get even if the waves look bad so you can get used to paddling and being in the water. When you start going more and you're around others read up on the 'rules of the road' and etiquette. Most of all have fun.