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While there are a variety of causes of "pink eyes" (allergy, viruses, and irritation from smoke, smog, dust, etc., just to name a few), most doctors, parents, and daycare/school teachers use the term "pink eye" to refer to infectious (contagious) bacterial infection of the conjunctivae (the membranes lining the inside of the eyelids and eyeball). It is one of the leading causes of "being sent home from daycare/school" and for good reason. The bacteria are right there on the outside of the body and are readily spread to toys and others by the rubbing hands of the child and the cleaning hands of the caretaker.
Bacterial conjunctivitis is treated with a prescription topical antibiotic (in drop or ointment form), and the child generally can return to school the day after beginning the therapy, once improvement is seen.
But just a word of caution: If other symptoms like fever, "runny nose", cough, and rash also exist, your child may need an oral antibiotic, as well. Since "pink eye" is a topical antibiotic-requiring bacterial infection, these other symptoms may very well indicate spread of the bacteria to other areas that the eye drops/ointment can't reach! Your doctor should advise you if such an oral antibiotic is needed.
Medically reviewed by Margaret A. Walsh, MD; Board Certification in Pediatrics