Scientists have transformed a regular sunscreen into a cooling lotion.

Protecting the skin from ultraviolet radiation using sunscreens has long become a standard practice. Unfortunately, these products do not have the ability to cool the skin.

Researchers from China have introduced a new cream formula featuring radiation cooling technology. They did not require new ingredients but worked with existing ones at the nano level. An article detailing this development has been published in the journal Nano Letters.

Radiation cooling functions by reflecting or emitting heat through a special coating, which lowers the temperature of the objects beneath it. This technology is already being utilized to create cooling fabrics and coatings for buildings. In some methods of radiation cooling, titanium dioxide (TiO₂) is used for heat dissipation.

This same material acts as a component in mineral sunscreens that reflects ultraviolet radiation; however, the typical particle size of TiO₂ cannot provide cooling effects.

A team of chemists led by Rufan Zhang (Rufan Zhang) adjusted the size of the nanoparticles so that the product could simultaneously protect the skin from UV rays while cooling it. The cream contains titanium dioxide particles of various sizes: 1-3 micrometers, 200-300 nanometers, and 10-20 nanometers.

The prototype cream consists of six components: nanoparticles of TiO₂, water, ethanol, moisturizer, pigments, and a cosmetic silicone polymer — polydimethylsiloxane. The scientists achieved a formulation that reflects not only ultraviolet radiation but also solar heat, providing a cooling effect.

The new formula demonstrated a sun protection factor SPF of around 50, water resistance, and maintained effectiveness even after 12 hours of simulated sunlight exposure using a xenon lamp. Furthermore, tests on animals and humans showed that the product does not cause skin irritation.

In hot and humid weather conditions, the test sample cream was able to cool the skin of participants by six degrees Celsius compared to bare skin and by three degrees compared to creams already available on the market.