Now, when we talk about food sensitivities, we're talking about several groups of foods. One group is foods that you should never, ever eat. Another group is foods you do eat sometimes and they cause problems, but you can limit them or choose to just go off of them for an extended period of time. There are other foods you can also rotate in and foods that you have no problem eating whatsoever. However, in order to get a picture of what these foods are, you can benefit from testing.
Cyrex Labs, one of the clinical lab testing services we work with, offers a variety of testing (arrays 3 and 4 are highly recommended for showing gluten sensitivity as well as other food sensitivities). We also recommend looking at ALCAT testing, which looks at your white blood cell response to certain foods. These testing options are an investment - but they're much cheaper in the long run than having to pay to treat food sensitivities and food allergies.
In addition to testing, you also need to be observant of your body's responses to certain foods. This takes time, but it's well worth the effort. Once you get these foods out of your body, you'll be healthier all around and more importantly, will feel better.