The four month old baby giggled, kicked, and drooled as we laid her onto the exam table. She was a healthy baby coming in to our pediatric clinic for a well child check up. Around 4-6 months of age, we recommend the introduction of solid foods to parents, so I discussed this with mom. My attending (boss) physician expounded and said that to avoid allergies, first feed the baby egg yolk which is less likely to develop allergies and then progress to egg whites once that goes OK.
As an immunology PhD student, I stood behind her and scratched my head. I wasn’t aware of any evidence supporting eating egg yolks before egg whites. Apparently, this used to be part of American Academy of Pediatrics guidelines, but newer guidelines state there is no good evidence for this practice. Furthermore, there was an interesting study in the New England Journal showing that delaying introduction of peanuts actually increases the risk of peanut allergy.
After our encounter, I asked the pediatrician, where does the recommendation to eat egg yolks first come from? She replied, “Hmm, that’s a good question. I guess we’ve just always done it that way. Not sure where it came from.” And so an old wives’ tale begins.