New EVMS research hints that a common ingredient in sunscreens may compromise the body’s immune system.

This is the first large-scale human study to investigate the association between benzophenone-3 (BP-3) and white blood cell counts. The research demonstrated that high concentrations of BP-3 were associated with significantly lower white blood cell and neutrophil counts, says researcher Nargiza Sadr, a third-year medical student.

Neutrophils are a kind of white blood cell that act as the immune system’s first line of defense against infection. Low levels of neutrophils can make the body more susceptible to infection.

"Our findings highlight a potential immunological effect of BP-3 that warrants further investigation,” says Sadr, lead author on the study published May 21, 2024, in the journal Skin Research and Technology. “Given the widespread use of BP-3 in sunscreens, understanding its impact on human health is crucial."

Sadr conducted the research with Rehan Qayyum, MD, Harry H. Mansbach Chair in Internal Medicine and Professor and Chair of Internal Medicine. Their extensive study utilized data from the National Health and Nutrition Examination Survey (NHANES), which ran from 2003 to 2016 and included 16,959 participants.

Their examination of the NHANES data found that higher urinary concentrations of BP-3 were associated with significantly lower total white blood cell count and neutrophil counts. The study controlled for factors such as age, gender, race, body mass index (BMI), smoking status, education level, income, survey cycle, and season.

Sunscreens play a critical role in protecting against harmful ultraviolet (UV) radiation, which can lead to sunburn, skin aging and skin cancer. BP-3 is a widely used organic filter in sunscreens due to its ability to provide effective UV protection without leaving a white cast on the skin.

“Despite BP-3’s widespread use, concerns have been raised about its potential systemic effects, including hormone disruption and immune system impacts,” Dr. Qayyum says.

This research contributes to the growing body of evidence regarding BP-3's biological effects. Though the use of BP-3 has been declining, it remains a common ingredient in sunscreen formulations.

“While previous animal studies have shown mixed results, this is the first large-scale human study of its kind,” Sadr says, “providing important insights for public health and regulatory considerations.”

While the research is alarming, Dr. Qayyum is careful to note that sunscreens are essential to protecting us from the harmful effects of the sun.

“Sunscreens are still important,” he says. “We just need to understand the ones we use better, and we need to find better ones.”