Reaching for Tylenol when baby is fussy? Here's some information worth knowing. A baby's liver isn't fully mature until around 2 years old Meaning their ability to process certain substances is still Exposure to acetaminophen and all its metabolites upon 10, 15, and 20 mg kg intravenous acetaminophen in very preterm infants Pediatric Research Tylenol And Alcohol: Dangers, Safe Alternatives & Treatment Yes there is good evidence that acetaminophen (the active ingredient in Tylenol) can deplete glutathione under certain conditions. But whether that matters depends on dose, duration, and individual factors.