There's multiple studies that directly contradict the author's theory but none that support it. His theory is that early peanut butter exposure increases risk of developing a peanut allergy due to some batches containing a peanut fungus.

Here are studies showing the opposite - that early exposure to peanut butter decreases the likelihood of developing a peanut allergy:

LEAP trial: Early peanut consumption (via peanut butter/Bamba) reduced allergy by 81% at age 5.

LEAP On: Protection persisted even after a year of avoidance.

LEAP Trio: Protection lasted into adolescence (only 4.4% developed allergy).

CHOP 2025 study: Population level allergy diagnoses dropped after guidelines encouraging early peanut introduction, which was primarily in the form of peanut butter.

[1] https://www.nih.gov/news-events/nih-research-matters/providi...

[2] https://www.niaid.nih.gov/news-events/introducing-peanut-inf...

[3] https://www.chop.edu/news/childrens-hospital-philadelphia-re...