Background: Children do not always outgrow hen's egg allergies in early childhood. Because egg yolks are less allergenic than egg whites, we performed an oral food challenge with heated egg yolk slightly contaminated with egg white (EYSEW OFC) in infants allergic to hen's egg. We hypothesized that the EYSEW OFC results would predict the egg allergy's natural course. Methods: We retrospectively reviewed participants with hen's egg allergy who underwent their first EYSEW OFC at 12-23 months of age between 2004 and 2010. Participants who passed the first EYSEW OFC were defined as EYSEW-tolerant, and participants who failed the OFC were defined as EYSEW-reactive. Participants who passed the EYSEW OFC underwent an OFC with half of a heated whole egg (WE OFC). Participants who passed a WE OFC were defined to be heated hen's egg-tolerant. Participants who failed the EYSEW OFC or the WE OFC underwent another OFC at least 6 months later. We compared tolerance to heated hen's egg at 36 months after the first EYSEW OFC between EYSEW-tolerant and EYSEW-reactive participants. Univariate and multivariate logistic regression analyses were conducted. Results: Of the 197 included participants (median age: 18.3 months; range: 12.1-23.8 months), 179 (90.9 %) were EYSEW tolerant and 18 (9.1 %) were EYSEW reactive. At 36 months after the first EYSEW OFC, 164 EYSEW-tolerant (91.6 %) and 12 EYSEW-reactive participants (66.7 %) achieved heated hen's egg tolerance. In the univariate logistic regression analyses, EYSEW-reactive participants (crude odds ratio [OR], 5.5 [95 % confidence intervals [CI], 1.8-16.6]; p = 0.003) and those with baseline egg white sIgE levels (crude OR: 3.9 per ten-fold increase [95 % CI, 1.5-10.2]; p = 0.005) had greater odds of persistent allergy to hen's egg at 36 months after the first EYSEW OFC. In a multivariate logistic regression analysis after adjustment for baseline egg white sIgE, EYSEW-reactive participants had greater odds of persistent allergy to hen's egg than EYSEW-tolerant participants (adjusted OR: 4.6 [95 % CI, 1.5-15.0]; p = 0.003). Conclusions: Classifying infants who are allergic to hen's egg into EYSEW tolerant and EYSEW reactive groups was useful in determining prognosis.