When my daughter was about 16 she was suffering from various problems, which it was suspected were caused by an allergy. After visiting a private hospital and seeing one of the leading food allergy specialists, (at that time the notion of food allergy was poo-poohed) she was put on a very strict exclusion diet. She was, after 3 weeks allowed to add a limited list of foods, and she did react after a time to various ingredients, but the most startling food she ate was a steak - within half an hour she was just fast asleep. Certain items made her joints ache, and dairy was a definite food which caused problems. She went on to use goat's milk, and a limited diet and there was a massive change in her medical problems. She still uses goat's milk, it is much nicer and easier to obtain than it used to be, and still has reactions to certain foods, but now it causes irritable bowel symptoms, rather than joint problems.