Many of us have experienced one of our eyes becoming suddenly red and irritated. Sometimes it can be easy to pinpoint the cause; maybe something got into the eye or you were unable to dodge your toddler’s finger as it darted into your eye.

However, the redness often comes about with no obvious inciting factor.

We see many patients who come into the office thinking they might have pink eye.

What is pink eye, and what causes it?

Pink eye is actually a rather broad term that encompasses a variety of conditions. What immediately comes to mind when most people think of pink eye is something called bacterial conjunctivitis.

This is an acute infection; the eye is red, the eyelids are often swollen, and there is a whitish-yellowish discharge present. Bacterial conjunctivitis is much more common in children than adults and is easily spread by physical touch.

The conjunctiva is a clear tissue that lies on top of the sclera, the white part of the eye. When it is inflamed, you have “conjunctivitis.”

A bacterial infection is just one thing that can cause this. You can also have a “pink eye” that is a response to a viral infection and is fittingly called viral conjunctivitis. This might occur at the same time as, or right after having, a common cold.

Viral conjunctivitis signs and symptoms are very similar to those of bacterial conjunctivitis: The eye is red and the eyelids might be swollen.

The eye will tend to tear a lot with a viral conjunctivitis and feel scratchy or irritated.

Both viral and bacterial forms might spread from one eye to the second eye within a few days, and we always recommend washing hands, towels, pillowcases, etc.

A third cause of a “pink eye” is an allergic conjunctivitis. This condition looks a lot like a viral conjunctivitis, with a red eye, swollen eyelids and a watery discharge.

However, the distinguishing factor is often itching of the eye itself. This can range in severity and can be caused by a variety of allergens.

These are just a few of many causes of a “pink eye,” and they are all treated differently.

Pinning down the cause of a “pink eye” can be difficult, and it is always a good idea to pay your eye care professional a visit any time you develop a red, irritated eye.

Caroline Bundrick, O.D. is an optometrist practicing at Darling Eye Center, with offices in Bluffton and on Hilton Head Island.