City Lights Are Making Allergy Season Longer

Artificial nighttime lighting in cities is stretching allergy seasons by about two months compared to rural areas. Plants rely on darkness as a signal to stop growing and making pollen. But streetlights and buildings confuse that signal, keeping plants in growth mode longer. A study of pollen data from 2012 to 2023 across the Northeast shows urban allergy seasons start three weeks earlier and end much later than in the countryside.