Neonatal jaundice is usually mild and temporary, but in some cases it can reach dangerous levels if not treated in time. To avoid complications, such as neurological damage, clinical practice relies on early diagnosis and the use of controlled phototherapy devices, which emit light within a specific range and at a well-defined intensity.
Researchers from the Universitat Politècnica de València, the Francesc de Borja University Hospital in Gandia, and the La Ribera University Hospital, through the Fisabio Foundation, have found that sunlight passing through home windows is neither a safe nor a recommended alternative for preventing or treating neonatal jaundice, a condition that affects more than half of all newborns.
However, in everyday practice, it remains common to informally recommend “putting the baby in the sun, near the window.” Although guidelines do not recommend sun exposure, this practice remains common for preventing or treating jaundice.
In their study, the research team analyzed how sunlight behaves as it passes through different types of glass commonly found in homes—they evaluated up to seven different types of glass. They concluded that, although the light entering through windows maintains a high intensity in the blue spectrum—the spectrum used in medical treatments—it does so uncontrolled and accompanied by potentially harmful radiation.
The team measured solar irradiance under different conditions and found that, 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,” notes Jesús Alba, a researcher at the Gandia Campus of the Universitat Politècnica de València.
Furthermore, the study reveals that standard glass does not effectively filter other types of radiation, such as ultraviolet (UVA) or infrared. This can pose an added risk, as these types of radiation offer no therapeutic benefits and can cause overheating, dehydration, or damage to the skin and eyes.
Unlike medical devices, which allow for dose adjustment and patient protection, sun exposure depends on multiple variable factors such as the time of day, weather conditions, the orientation of the home, and the distance from the window.
“This lack of control makes it impossible to guarantee both the efficacy and safety of this practice. Residential window glass allows very high levels of solar irradiance to pass through, with a broad spectrum that includes UVA and infrared radiation, and blue irradiance several times higher than that used in phototherapy, but without selectivity or dose control. Therefore, exposure to sunlight through a window is not recommended as a preventive or therapeutic method for neonatal jaundice,” emphasizes José Miguel Sequí Canet, a pediatrician at the Francesc de Borja University Hospital in Gandia.
The study concludes by highlighting the importance of following established clinical guidelines, based on bilirubin screening and the use of regulated phototherapy when necessary.
The idea for the project and this study originated with Safor Salut, a cooperation program involving key players in the Valencian health innovation system in the La Safor region and its surrounding areas (UPV, Fisabio, and FAES). It was developed under the 2023 call for proposals of the Polisabio program—promoted by the UPV and Fisabio—and integrated into UniSalut, the collaborative alliance between the Fisabio Foundation and the Valencian universities (UPV, UJI, UMH, and, most recently, CEU Cardenal Herrera).
Further information:
Sequí-Canet JM, Alba Fernández J, Del Rey R, Angelats Romero CM, et al. Luz solar a través de los acristalamientos del domicilio y prevención de la ictericia neonatal. Anales de Pediatría. 2026. doi:10.1016/j.anpedi.2026.504206