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Curiosities: Why do the blue eyes of babies often turn brown?

June 1, 2009

Melanin is the pigment that makes body parts dark, said Burton Kushner, professor of ophthalmology at the School of Medicine and Public Health.

“Melanin makes freckles brown, hair brown and pigmented races brown, and it can make the iris brown as well. Melanin is not fully developed in newborn babies, so the iris is relatively devoid of whatever melanin pigment it will have, and that gives the eye its baby-blue eye color.”

But by nine months, or 12 months at the latest, the iris of a child destined to be brown-eyed has finished producing melanin, which causes the eye to turn brown.

The reverse process does not happen, says Kushner, a specialist in pediatric ophthalmology: Brown eyes do not turn blue as a baby grows.