There are some side effects caused by this eye drop mainly at starting like allergic reaction, pain in eye, irritation, redness etc. Long term side affects or any drug interactions are not noticed frequently. If you are using another eye drop maintain a 15min gap in between. If you are using contact lens please remove it before the use of eye drops. Though the chance of long term side effects are very low if you develop blurred vision, rash, pain or red eye, eyelid oedema, pruritic eye please contact your health provider. About the storage procedure refer to storage information printed on the package. Protect from light and moisture. Protect ointments from freezing. Some preservative-free drops that come in single-use vials/droppers should be discarded either immediately after use or up to 12 hours after opening. Check your product package to see when you should discard your preservative-free product. About the Flogel eye drop store below 25°C in a dry place. Do not use for more than 30 days after first opening the container.Do not touch the tip of the container to any surface. Replace the vial cap after use.  So as the drop is opened for 3monthes please discard the drop and use a new one.