All eye drops have expiration dates printed on them. It is important to use your medications according to how they were prescribed, and not permit the dropper tip to become contaminated. Medications may lose potency, change chemical composition, become contaminated, or have bacteria grow in them over time. For these reasons it is good idea to discard them after they expire (contact a local pharmacy to determine whether your medications can be safely thrown away in your household trash). If the drop becomes uncomfortable, changes color, or if the area under the cap becomes dirty, you should discard the bottle.