DS has eczema, asthma and a multitude of food allergies, and I find it crazy that they have told you that results wouldn't be reliable in an atopic child, if he was not atopic you wouldn't need the tests.
I think ANY test has certain degree of unreliability but I think that you will agree with me that it's better to know half truths than nothing at all.
DS had 3 tests:
-ELISA. Expensive, and IMO the most inaccurate of the 3, but the only commercialy available at the time we were desperate for an appointment that took 18m to take place. It wasn't a waste of money though, it gave us a clear idea of which could be the most problematic elements.
-RAST. More accurate, and in our experience the most reliable. We ordered RAST tests for the foods that scored the highest grade in the ELISA test. The results confirmed allergies to all the elements on the list.
-Kinesiology. Well, I make the apointment several times and cancelled afterwards because I couldn't trust it, at the end I decided to give it a try mostly thinking in a possible alternative treatment to help DS instead of "confirming" what we already knew. Kinesiology tests "results" were almost the same as the ELISA test. No treatment given just strongly advised to avoid those allergens.
-Skin prick. The test prefered by our NHS consultant as the most acurate and the only one he would accept as reliable. We were 18m in the waiting list for this one. Funny thing with this test is that it confirmed the results of the RAST test but denied the allergy to milk, which incidentally is the food for which DS shows the most immediate and noticeable reaction!
The most annoying thing of all this process was to have the doctors saying that these or that tests results were not reliable and at the end, they were. We don't consider the money spent in test a waste, quite the contrary, if we had just waited for the skin prick test to take place DS would have had to go through another 18m of misery, which was avoided thanks to the first "inaccurate test"'s result.