Exposure to sunlight through windows puts the baby at risk of dehydration and skin damage

Researchers from the Universitat Polytechnica de Valencia, Francesc de Borja University Hospital in Gandia and La Ribera University Hospital, through the Fisabio Foundation, have found that sunlight passing through windows in homes is neither a safe nor recommended option for preventing or treating neonatal jaundice, a condition that affects more than half of all newborns.

Newborn 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 depends on early diagnosis and the use of controlled phototherapy devices that emit light within a specific range and at a well-defined intensity.

However, in everyday practice, it is common to informally advise “put the baby near the window, in the sun”. Although guidelines do not recommend exposure to sunlight, the practice is still common to prevent or treat jaundice.

In their study, the research team analyzed how sunlight behaved when passing through different types of glass commonly found in homes – up to seven types in total. They concluded that although the light entering through windows maintains high intensity in the blue spectrum – which is used in medical treatments – it is so uncontrolled and accompanied by potentially harmful radiation.

The researchers measured solar radiation under various conditions and found that, outdoors, blue light can reach levels eight times higher than the lights used in intensive phototherapy.

“When passing through glass, 70% to 90% of the light still reaches the interior, which means that a newborn baby exposed near the window could be exposed to very high levels of radiation, which are difficult to control,” says Jesús Alba, a researcher at the Gandia campus of the University Polytechnic de Valencia and author of the study.

Additionally, studies show that standard glass does not effectively filter other types of radiation, such as ultraviolet (UVA) and infrared radiation. This may pose an additional risk, as these forms of radiation provide no medical benefit and may cause overheating, dehydration, or damage to the skin and eyes.

Unlike medical devices, which allow the dosage to be adjusted and the patient’s safety, sun exposure depends on many variables, such as time of day, season, orientation of the house, and distance from the window.

This lack of control makes it impossible to guarantee the efficacy or safety of this practice. Residential glazing allows very high levels of solar radiation to pass through with a broad spectrum that includes UVA and infrared radiation, and blue radiation several times higher than that used in phototherapy, but without selectivity or dose control. For this reason, exposure to sunlight through a window should not be used as a preventive or therapeutic method for treating neonatal jaundice.”

José Miguel Sequi Canet, pediatrician, Hospital Francesc de Borja in Gandia

The study concludes by highlighting the importance of following established clinical guidelines, including bilirubin screening and regulated phototherapy when necessary.

The project and the idea of ​​this study originated from Safor Salut, a collaboration program between key players in the Valencian health innovation system in the La Safor region and its surroundings (UPV, Fisabio and FAES). It has been developed under the 2023 call for proposals of the Polisabio program – promoted by the UPV and Fisabio – and is part of Unisalut, a collaborative alliance between the Fisabio Foundation and Valencian universities (UPV, UJI, UMH and, most recently, CEU Cardenal Herrera).