SUN CARE 29
The critical role of SPF synergistic agents
Claire Cai, Kaia Kang - Aegis Beauty Solutions ABSTRACT
The pursuit of higher sun protection factors (SPF) and broader spectrum protection has evolved beyond simply stacking of ultraviolet (UV) filters. Contemporary sunscreen research increasingly emphasizes advanced formulation strategies aimed at maximizing the performance of individual protective components. This article examines a critical underappreciated class of ingredients — SPF-boosting agents, also referred to as synergists. By systematically outlining five key mechanisms of action — namely, film formation, dispersion optimization, light scattering, biological activity modulation, and photo stabilization — this paper demonstrates how these agents function synergistically with primary UV filters to achieve more efficient, stable, and safe photoprotection systems
Growing consumer awareness of photoaging and skin cancer has driven an increasing demand for sunscreen products that offer high levels of protection, superior sensorial performance, and a strong safety profile.1 However, simply increasing the concentration
of organic or inorganic UV filters often results in undesirable consequences, including an unpleasant skin feel, elevated risk of irritation, compromised formulation stability, and increased production costs. As a result, cosmetic scientists have increasingly
focused on synergistic ingredients within sunscreen formulations. Although these components typically exhibit little to no intrinsic UV-absorbing capacity, they can substantially enhance the overall efficacy and stability of sunscreens through a combination of physical, chemical, and biological mechanisms. Collectively referred to as SPF synergistic
agents, or boosters, these materials play a critical role in modern sunscreen design. This article systematically examines their underlying
mechanisms of action and evaluates their practical benefits in advanced sunscreen formulations.
Film-forming agents: improvement of UV filter distribution on the skin Film-forming agents enhance SPF performance by promoting the formation of an uniform, continuous, and adherent film on the skin surface.2 This film plays a critical role in optimizing the spatial distribution of UV filters by retaining them at the site of application, reducing inhomogeneities arising from skin microrelief, perspiration, or mechanical abrasion. As a result, a more consistent, durable, and reliable level of photoprotection is achieved. In the blank control (BC), neither a soft nor a
hard film-former was incorporated, resulting in a SPF value of 25. In the No Soft Film-Former (NS) group, only 1002A was included, whereas in the formulation No Hard Film-Former (NH) group, only PS15 was added. In the experimental group (EG), both 1002A and PS15 were incorporated.
TABLE 1: FORMULATION DETAILS AND CORRESPONDING SPF VALUES OF DIFFERENT SUNSCREEN SYSTEMS
Formulation PS15 (Polysilicone-15)
SF-1002A (Trimethylsiloxysilicate) SPF value (in vitro)
Increase versus baseline
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BC - -
32.18 -
NH 2 -
39.98 24%
NS - 2
36.07 12%
EG 2 2
51.22 59%
The influence of different film-forming agents
on the SPF performance of the formulations was systematically evaluated. PS15 functions as a silicone-based soft film-former and also serves as a UV filter. In contrast, SF-1002A is a silicone resin recognized for its ability to form a more rigid and resilient ‘hard’ film on the skin surface. As shown in Table 1, both film-formers
significantly enhanced the SPF of the formulations. PS15 exhibited a more pronounced SPF-boosting effect, which may be attributed to its superior skin conformity and its ability to promote a more uniform initial distribution of UV filters. SF-1002A, while providing a comparatively lower SPF increase, likely offers advantages in terms of related to water resistance and resistance to mechanical abrasion. Notably, the formulation containing both PS15
and SF-1002A demonstrated substantially higher SPF performance than those containing either film-former alone, indicating a synergistic effect between soft and hard film-forming technologies. Accordingly, formulators may tailor the
selection and combination of film-formers based on the intended product positioning, such as daily- use sunscreens versus sport or water-resistant applications.
Dispersion optimization agents: enhancement of solubilization and molecular dispersion For organic sunscreen systems, photoprotective
June 2026 PERSONAL CARE MAGAZINE
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