The first antibiotic to be sold by pharmacies without prescription has little effect, a study says.
Chloramphenicol is used to treat bacterial conjunctivitis
One in eight children develop the eye condition conjunctivitis each year and in many cases family doctors use chloramphenicol to treat it.
But an Oxford University study in the Lancet said the cure rate was nearly the same if the drops were used or not.
Researchers urged parents to wash children's eyes with warm water rather than use the drops.
The Medicine and Healthcare products Regulatory Agency, the UK drugs regulator, announced earlier this month the eye drops would become the first antibiotic to be made available without prescription.
The move caused alarm among doctors who said increased use of antibiotics could lead to resistance.
Report author Dr Peter Rose added: "We have shown that symptoms resolve without antibiotics in most children with acute infective conjunctivitis.
"The health economic argument against antibiotic prescription for acute conjunctivitis is compelling.
"And with antibiotic resistance a growing problem, parents should consider treating the condition themselves unless symptoms persist for more than a week."
The report said standard practice for doctors was to prescribe chloramphenicol as they often had problems differentiating between a viral cause of the condition and bacterial cause.
More than 300 children took part in the study, with half of them being given chloramphenicol, while the others received placebo eye drops.
After seven days 86% of children given chloramphenicol were cured compared to 83% in the placebo group.
Even in children who had a bacterial infection, the cure rate did not differ significantly, 85% for the chloramphenicol group, compared to 80% for the others.
Dr Peter Swinyard, a member of the British Medical Association's GPs committee, agreed it was often hard to differentiate between viral and bacterial conjunctivitis.
But he added it was still worthwhile using antibiotics for infective bacterial conjunctivitis.
David Pruce, of the Royal Pharmaceutical Society of Great Britain, said the decision to allow an antibiotic to be sold over-the-counter was an important milestone.
But he added: "The society believes that a more in-depth analysis of this paper and more comprehensive research and data is required before any consideration is given to whether or not there needs to be a change in pharmacy or medical practice."
And the MHRA said the findings were interesting, but the regulator was convinced of the health benefits and there were no plans for a change in position.
"Chloramphenicol has been used for more than 50 years, its safety and effectiveness in the treatment of bacterial conjunctivitis is well established."