Today's lovefood newsletter, which is very much pitched at foodies, rather than health obsessives, had a brief article today on food intolerance testing which may be a sign of the general public's increasing awareness around food intolerances and the benefits of avoiding certain foods.
I have to say I personally have mixed feelings around the tests - they certainly do pick up food reactions and so can help you avoid problem foods, but there are several different types of immune reactions to foods so just because a food doesn't come up on the test doesn't mean it definitely isn't a problem for you. For example these tests don't pick up if you have coeliacs disease, but also it has recently been suggested that other types of gluten intolerances can also be missed. I can vouch for this as I have a very clear gluten intolerance that has never been picked up in testing, on the flipside testing has made me aware of some other foods I needed to avoid that I hadn't worked out on my own.
As first principles I think it's worth everyone following a basic elimination diet for 3 weeks to check for reactions to the obvious culprits. Three weeks off gluten, dairy, eggs and soy is a good place to start, then reintroduce each one separately for three days. You're looking for changing symptoms both when you give up the food and when you reintroduce it. If you can't face giving them all up simultaneously just try one at a time for two weeks at a time, or if you're feeling particularly motivated combine it with a detox diet (I usually do the Carol Vorderman detox), which will naturally exclude most allergens and give you a good diet overhaul at the same time.