Writing in its international patent, Unilever said the two-step application method offered the “synergistic benefit” of high Sun Protection Factor (SPF) and UVA protection factor (UVAPF). The method comprised of washing the skin with a cleansing composition comprising water-soluble sunscreens, in bar or liquid form, followed by applying a leave-on sunscreen composition to the skin as a cream, gel or lotion.
Unilever said the two products could be offered to consumers in “kit” form with instructions for use.
Unilever said that whilst most sun protection offerings were in leave-on formats, like creams, lotions and gels, it was also possible to offer protection via wash-off products like soaps, face wash or body wash. However, offering adequate protection in a wash-off product remained complicated, the company said.
“It is an extremely difficult challenge to deliver sunscreens onto skin when the primary purpose of wash-off products is to remove the dirt and oils from the skin surface and together with that, the actives in the wash-off products are also highly likely to get washed away. Thus, enhanced deposition of actives through wash-off products is an ongoing challenge,” Unilever wrote in its patent filing.
Scientific teams at Unilever therefore set out to find a way to counter this problem and after “extensive experimentation” they “hit upon a unique two-step method”.
Cleansing and protecting
The company said it had developed a wash-off composition that deposited high levels of sunscreen whilst maintaining good lather on the skin, and enhanced deposition of the protective actives was seen in both solid bar and liquid cleansing formats. Ultimately, the company said the cleanser could also be developed in the form of a shampoo or conditioner as well, offering photo-protection to the hair and scalp.
The cleansing composition incorporated both UVA and UVB water-soluble sunscreens alongside higher levels of surfactant and a cosmetically acceptable carrier that was applied and then rinsed off with water. This cleansing step was then followed by the application of a leave-on composition comprising a sunscreen, preferably an organic UVA sunscreen and organic UVB sunscreen combined. The leave-on could be in the form of a liquid, lotion, cream, stick, gel or spray for either the skin, scalp or hair and include additional actives offering a fragrance, colour or skin soothing and healing properties.
“Surprisingly, specific combination of the sunscreens ensures that they deposit in much higher amounts than is general expected from rinse-off products, in such a way that the deposited sunscreens interact synergistically with the sunscreens applied from the leave-on composition to provide the enhanced SPF and UVAPF benefit,” Unilever wrote.
The resulting double-application, it said, ensured SPF protection of 15 and above, preferably as high as SPF 50, and SPF 100 “in optimum cases”. The double application resulted in a UVAPF of between 4-16 in the current invention, but could be pushed as high as 40, Unilever said.
WIPO International Patent No. WO/2022/253896
Published on: December 8, 2022. Filed on: June 1, 2022.
Title: “A method of providing high SPF to a topical surface of a body”
Inventors: Unilever – PGR. Lahorkar, R. Perumal and AA. Vaidya