Microbial keratitis is an ophthalmic emergency. We present two cases of microbial keratitis in which inappropriate chloramphenicol use delayed diagnosis and hence prompt management. For one patient, the result was loss of the eye, and for the other, a child, lifelong reduced vision from corneal scarring. The first case was a 69‐year‐old woman who presented with a three‐week history of a red, watery right eye and gradually reducing vision. She had been self‐treating with chloramphenicol drops and ointment, obtained from her pharmacist without medical consultation.