I am allergic to certain food types and I am worried about going to Thailand.

We already have a section which will help you with this. The Thai word for "allergic" is "pare".

Men say: "Phom pare....."
Women say: "Di-chun pare..."

http://www.learningthai.com/allergic.html

This page has sound clips so that you can practice speaking and also a link to print the phrases out in Thai.