Colief infant drops work by breaking down the majority of the lactose in your babys usual milk before they are fed making the feed more easily digestible studies have shown that the hours of crying may be greatly reduced when babies are fed their usual milk when it has been treated with colief infant dropsthe active ingredient in colief is lactase an enzyme which occurs naturally within the bodyyou can use colief every time you feed your baby until the baby is approximately 3 4 months old