The long-term moisturizing effects of cosmetic formulations may be more effective if applied in a cream rather than a serum format, according to scientists. Researchers from the University Hospital of Liège, Belgium, investigated the effect of the concentration of active ingredients and the application medium on the efficacy of an anti-ageing formulation containing marine extracts.
Serums for short-term effects, creams for the long term
The study, published in this month's International Journal of Cosmetic Science, included both a medium-term trial where test formulations were applied to volunteers twice daily for two weeks and a short-term trial which investigated the effect of one single application of the formulations.
The medium-term trial involved twelve volunteers who applied the four test formulations of two serums and two creams at 7.5 and 10% concentrations, and the two controls--the serum and the cream with no marine extract.
Although the serums showed good results immediately after application, the creams delivered better long-term results, particularly in terms of hydration, according to the scientists led by E. Xhauflaire-Uhoda.
The team hypothesized that the immediate rise in hydration brought about by the serums is likely to be due to the higher water content and the absence of film-forming hydrophobic compounds. In contrast the creams contain hydrophobic compounds that may help to limit water evaporation through the skin barrier.
Similarly, with regards to the formulations' firming effect on the skin, the serum produced the best immediate results. The positive effect of the serum on skin firmness also continued over time. The team put the swift and intense effect of the serum down to more hydrophilic agents that may facilitate the diffusion of the active compounds, in contrast to the hydrophobic compounds in the cream. Marine extract improved hydration and firmness
Furthermore, the team noted the effect of the concentration of the active marine compound on the efficacy of the formulation. The 7.5 and 10% serums and creams performed better than those devoid of the marine extract, and the 10% serum appeared to be more active than the 7.5%.
However, no firming effect remained 3 days after treatment ended with any of the formulations--the team suggested that a two-week period is perhaps too short to highlight such an effect.
Application medium influences product efficacy
The study highlights the importance of the application medium on a product's efficacy and the subtleties of these effects.
A formulator's choice of application medium may depend on the desired effect for the product. For example, a product designed to provide immediate moisturizing benefits may require a different medium to one formulated to provide long-term hydration.
Source: E. Xhauflaire-Uhoda, K. Fontaine and G.E. Piérard, "Kinetics of moisturizing and firming effects of cosmetic formulations," International Journal of Cosmetic Science, Vol 30, 131-138
Cosmetics Design-Europe.com, March 19, 2008