I believe the incident of false negative skin prick test, may vary according to allergen. For instance, dairy may have a false negative incident of x%. But, wheat may have a false negative incident of y%.
Even within "dairy", there are different types of casein, A1 and A2, for instance. So, if you skin prick test one of those, it may not apply to the other type of casein.
Same with wheat, sprouted wheat, GMO-wheat, etc. Also, the conduit substrate which preserves and imparts the allergen could deteriorate over time, based on many variables...
This report describes some of the various testing issues. http://findarticles.com/p/articles/m..._/ai_n14899860
This informative articles reports, "A negative prick skin or RAST test predicts with about 97% accuracy that the test food was not the cause of symptoms but only in atopic disorders and where immediate hypersensitivity food reactions are involved."
(which doesn't answer your question, lol)
Here is another report, specific to "milk", for example. "In the literature, the positive predictive accuracies of skin prick tests vary between 69 and 100% and the negative predictive accuracies between 20 to 86% for cow's milk."
Ah-ha, found this!
Skin Prick testing: Good for telling what you are NOT allergic to but not what you ARE allergic to (low positive predictive accuracy, good negative predictive accuracy). (Skin prick testing is not paid for by Medicare.
For milk and eggs, the testing results are approximately 50% false positive but less than 5% false negatives. For peanuts, 70% false positive and 10% false negative rate. No correlation between skin test size and severity of reaction. (Sporik R, et al. Clinical Exp Allergy 2000; 0:1540-6) View Abstract
Skin Prick testing to nuts � 46% of those tolerant to nuts had a positive skin prick test as only 0.5% of those clinically allergic to nuts had a negative test. (Clark at, Ewan PW. Clinical Exp Allergy 2003; 83 1041-45) View Abstract
This site seems to reference actual studies related to accuracy of different allergy testing alternatives. http://www.entusa.com/food_allergy.htm