The Coeliac Society produces a listing of all products which are gluten-free. This can be obtained from the Society but they do require a supporting letter from the General Practitioner before they will supply it. Tesco, Marks and Spencers and Sainsbury's all produce useful lists of products. There are also some excellent recipe books available. It varies with individuals.
Most parents try to be absolutely ruthless particularly in the early days of experimentation.
It would seem that after a period of time, several months, some people can get away with a small amount of material in their diet. We do not really know. Eggs, maize, bananas, nuts, chocolate, orange and lemon juice, apples, highly coloured foods have all come under suspicion in certain individuals. We would encourage parents or carers to work systematically and observe changes for themselves. The role of yeasts such as Candida is unclear.