I would start w/ the top 8 most common, start w/ milk and go down the list: milk, egg, soy, peanut, tree nut, wheat, fish and shellfish. He should not have had nuts or fish under 2 anyway, but if you've been feeding him them, stop for now. Cut out the milk, eggs, and soy for 2 weeks and see what that does. If he clears up, try them one at a time. If not, cut out wheat as well. If he clears after that, trial each 1 at a time. Feed him a little, just a few bites, the first day, if no reaction, then feed him a bunch for 2 days and then a normla amount after that. If no reaction after a week, then add the next one.If you are nursing, you should probably cut them from your diet as well. HTH!