BACKGROUND: Although allergists typically use allergen-specific IgE (sIgE) levels or skin prick test wheal sizes to identify food allergens that may provoke IgE-mediated food-induced allergic reactions, both tests have high rates of false positivity and mislabel patients who are tolerant as allergic to the food allergen. OBJECTIVE: To examine the accuracy of the ratio of sIgE to total IgE ("Ratio") in predicting the outcome of challenges performed to confirm the development of tolerance. METHODS: Medical records of children diagnosed with food allergy who participated in oral food challenge at an allergy outpatient clinic (2009-2013) were reviewed for IgE antifood serology and concomitant oral food challenge outcomes, which were analyzed for associations by using logistic regression models and receiver operator characteristics curves. RESULTS: The Ratio for participants who failed their challenge was higher than the Ratio of those who passed their challenge (failed 1.48% vs passed 0.49%; n = 195). Receiver operator characteristic curves showed that the Ratio was significantly more accurate than sIgE alone in predicting challenge outcome (Ratio 0.69 vs sIgE alone 0.55; P = .03). These trends were mostly associated with more persistent food allergens, such as peanut, tree nuts, shellfish, and seeds (failed 2.18% vs passed 0.41%; n = 93) (Ratio 0.81 vs sIgE alone 0.54; P < .01). CONCLUSION: Our findings suggest that the Ratio is more accurate than sIgE alone in predicting outcomes of challenges performed to confirm the development of tolerance to select food allergens, especially to peanut and tree nuts. The Ratio may be useful in identifying patients most likely to pass oral food challenge.