Before using natamycin, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. For keratitis, consider alternative medicine if no improvement in 7-10 days. After you apply this drug, your vision may become temporarily blurred. Do not drive, use machinery, or do any activity that requires clear vision until you are sure you can perform such activities safely.