My daughter has a spiked temperature and flushed face usually an hour after eating. The doctors can't diagnose what is wrong.?
Your daughter could be allergic to a certain type of food. Dairy, gluten, MSG (which is actually a neurotoxin, not an allergen), etc.
Try cutting out one thing at a time to see if her symptoms go away. Have her doctor's performed a scratch test on her? If not, you might want to request one.
Doctors do not find it hard to diagnose these conditions. You just have to consult them and do the tests as they prescribe.
Take her to an endocrinologist, it sounds like something metabolic. Look into Carcinoid Syndrome.