You can reuse most medicine droppers, but you must clean them before reusing or before storing them for later use. Left dirty, the remaining medicine will dry on the inside and outside of the dropper and be more difficult to remove as time goes by. In addition, handling medicine droppers exposes them to germs, even if the dropper does not directly contact, for example, the nose, eyes or mouth. This is another important reason you should clean medicine droppers before using them again for other medicines (or the same medicine later on).
Remove the rubber tip, if possible. Some droppers are easier to disassemble than others--don't force it. You can still clean the dropper even if you can't remove this (see the Tips section). Set the rubber tip aside. You will clean it separately.
Hold the dropper (sans rubber tip) under warm running water. Use a slender dropper brush to scrub inside the dropper. Add a tiny drop of mild dish detergent to the brush, if the grime on the dropper seems difficult to remove.
Rinse the dropper well by holding it under running water and allowing the water to flow through it.
Pour rubbing alcohol (or hydrogen peroxide--drug-store strength) into a shallow bowl, deep enough to submerge the dropper. This is to sanitize the dropper. Fill the dropper with the alcohol. Leave it in only for a minute (unless the dropper is glass, in which case you may leave it longer; rubbing alcohol can dry out plastic and rubber, however). Rinse the dropper well, inside and out, with warm water.
Place the dropper on a clean cloth to dry. Clean the rubber bulb tip by holding it under warm water. Use the slender brush to clean the interior. Rinse it well with warm water and flush it with rubbing alcohol. Rinse it again to remove traces of the alcohol (which could dry the rubber).