Gluten-free, casein-free foodstuffs (including ingredients and ready-made meals) are available from a wide range of suppliers (such as chemists and supermarkets) in the UK, the US and some other countries. Most (but not all) foodstuff labels state whether they contain gluten and/or casein.
Various support groups also produce advice about food content, gluten- and casein-free foods, together with special GFCF cookery books etc.
There are no formal qualifications for people using the gluten-free, casein-free diet since any individual, parent or carer can choose to follow the diet.
However, if you are contemplating such a significant change of diet, we recommend that you should seek advice from a responsible health professional such as a health visitor or GP. This may lead to a referral to a dietician – in particular one with experience of working with autistic individuals.
The British Dietetic Association has information about qualified dietitians in the UK.