The first immediate effect after administering iron is considerable mite fall. This high mite fall lasts for 1 or 2 days. If iron is administered again within a few days, the same substantial mite fall is observed again. This means that additional iron has exactly the same effect on the mite fall as formic acid, and an effect similar to that observed with oxalic acid and thymol treatment. On the page Effect of administering iron on mite fall - tick model you can read about why mites fall off bees after administering extra iron.
Additional iron also has an immediate effect on the behavior of the bees - they become more active. They fly more actively and they remove sick and weakened bees from the hive. After administering iron, the bees move off the flight shelf more quickly. For further information, see the information in the section News & other information.