Giving a baby a new food to try is fun, and it should be. The only concerns parents should have: finding their phones fast enough to document the funny faces and cleaning up the mess that might follow. Yet in recent years, scientific evidence has accumulated quickly on what foods to introduce when and how to best prevent allergies — leaving parents to keep track of it all. On Monday, based on a detailed review of all available evidence on the topic, the American Academy of Pediatrics published updated guidance on what works and what doesn’t when it comes to the prevention of food allergies and other allergic conditions. The new guidelines continue to liberalize the introduction of what are thought to be highly allergenic foods such as peanuts, fish, and milk.