When you work too hard or play too hard the surface of your eyes can sometimes become red and irritated. Smoke, sun glare, swimming, dust, smog or wearing contact lenses can all cause the blood vessels in the eyes to swell, making the eyes look red. The key active ingredient in Murine Clear Eyes is Naphazoline Hydrochloride which is a decongestant and vasoconstrictor that helps to reduce unsightly blood vessels to remove the redness and brighten eyes for up to 8 hours. Directions for Use Gently squeeze one or two drops into each eye up to four times a day, or as directed by your doctor. To avoid contamination, do not touch eye dropper tip to any surface.