Pink eye seems like a straightforward condition, yet it is more complex than you would think. Not all pink eyes are contagious and some can indicate truly serious conditions. How do you tell the difference?

Contagious pink eye comes on suddenly, sometimes associated with goopy discharge and often associated with other symptoms of illness like a runny nose or fever. Not all contagious pink eye infections need eye drops, though. If the eye is red but has no goopy discharge, drops won't help. Prescription antibiotic drops are only needed for goopy eyes. Children can return to school or daycare the next day if drops are being used and when the pink eye is improving if no drops are needed.

Because contagious pink eye is often associated with other symptoms, it is not surprising that one-third of young children with goopy eyes will also have an ear infection and benefit from oral antibiotics. If your child has significantly swollen eyelids, pain with eye movement or is seeming very sick, you should seek care immediately. A sinus infection can rarely invade the space around the eyeball (orbital cellulitis) and cause the eye to be pink. A large proportion of children with a pink eye, no goop and fever will also have a sore throat all caused by a virus called adenovirus. No specific treatment is needed for this one, but children must stay out of school until the fever is gone and the pink eye is improving.

Another cause of pink eye that is not serious is allergic pink eye. Often the eye is very itchy and there may be some clear or whitish, stringy mucus from the eye. Usually both eyes are affected when the cause is allergic. This cause can be managed with cool compresses, antihistamines such as Benadryl, Claritin or Zyrtec and occasionally with prescription eye drops.

Pink eye can also be due to an irritant. If your child touches something then rubs her eye, the eye can become irritated and look red for a couple of days but will rarely have discharge.

Occasionally a scratch to the cornea can be the irritant of sorts and this will cause the white of the eye to be pink as well. The doctor can test for this with a special dye and black light and treat accordingly.

When pink eye comes on more gradually or is associated with pain, it is very important to seek care. Some eye conditions like iritis and acute angle glaucoma present with a red eye.

One way to differentiate between infectious, allergic or irritant pink eye and one of these more serious causes is to note where the redness is located. In more serious pink eye, the redness is often more intense close to the iris and less so at the sides of the eye. The opposite pattern is seen in infectious or allergic pink eye.

Next time you think to call your pediatrician when your child has pink eye hoping for a prescription over the phone, know that not all pink eyes are alike and because some can be serious, having your child examined is quite important.