Researchers from the Universitat Politècnica de València, Francesc de Borja University Hospital in Gandia, and La Ribera University Hospital, working through the Fisabio Foundation, announced on Apr. 16 that exposing infants to sunlight through home windows is not a safe or recommended method for preventing or treating neonatal jaundice.
Neonatal jaundice affects more than half of all newborns and is typically mild and temporary. However, if left untreated, it can become dangerous and lead to complications such as neurological damage. Standard clinical practice calls for early diagnosis and the use of controlled phototherapy devices that emit light within a specific range and intensity.
Despite these guidelines, researchers said it remains common advice to place babies near a window in sunlight as an informal treatment for jaundice. The study analyzed how sunlight passes through seven types of household glass and found that while blue spectrum light—the kind used in medical treatments—does penetrate windows at high intensity, this exposure is uncontrolled and accompanied by potentially harmful radiation.
The research team measured solar irradiance under various conditions. Outdoors, blue light can reach levels up to eight times higher than those used in intensive phototherapy. "When passing through glass, between 70% and 90% of that light still reaches the interior, which means that a newborn exposed near a window can be exposed to very high levels of radiation that are difficult to control," said Jesús Alba, researcher at the Gandia campus of the Universitat Politècnica de València.
Additionally, standard glass does not effectively filter ultraviolet (UVA) or infrared radiation. These forms offer no therapeutic benefit but may cause overheating, dehydration or skin and eye damage in infants. Unlike medical devices—which allow precise adjustment—sunlight exposure depends on factors like time of day or distance from the window.
The study emphasizes following established clinical guidelines for screening bilirubin levels in newborns and using regulated phototherapy when necessary.
