Burning/stinging/irritation/redness of the eye, feeling as if something is in your eye, dry eyes, watering eyes, and increased sensitivity to light may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly. This medication may slowly (over months to years) cause brown discoloration of the colored portion of the eye (iris). If you are using bimatoprost in only one eye, only that iris may change color. An increase in eyelash number/length/thickness, darkening of the eyelashes/eyelids, or eyelid changes may also occur in the treated eye. These changes may be permanent, but the long-term effects are uncertain. Notify your doctor if this occurs, and schedule regular eye exams to monitor it. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if any of these unlikely but serious side effects occur: vision changes, eye pain/swelling, swelling/redness of the eyelids. A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.