The sun protecting perspective
The proderm story from April 2022 illustrates that herpes simplex can be caused by UV-radiation. Sun protection products may therefore be a suitable method to prevent the activation of herpes labialis.
How well UV filters work against the sun's rays is tested for lip products in the same way as for all other sun protection products. The sun protection factor is determined according to ISO 24444:2019 with a xenon arc solar simulator (300 W Multiport) on the back of 5 to 16 subjects. Up to 4 products can be investigated at the same time. One test area remains untreated and another is treated with a standard product.
In addition to that, manufacturers of sun protection products may gain extremely valuable insights by using Raman spectroscopy, e.g. for the in vivo determination of the amount of UV filters deposited on the lips after product application.
The moisturizing perspective
The evaluation of the moisturizing effect is another important parameter, especially for cosmetic leave-on products for lips as those often claim a moisturizing effect and thus protect against dry, cracked and sensitive lips. This can be established in a dermatological evaluation as well as with quantitative measurement methods.
In several studies at proderm, Raman spectroscopy was used to investigate how the proportion of certain molecules changes after several weeks' use of leave-on products compared with placebo. The focus here was on the water profile across the horny layer as well as on its NMF (natural moisturizing factor) and ceramide content.
In addition, stratum corneum hydration can be determined by means of a Corneometer and the lip barrier function by trans-epidermal water loss measurement with the Aquaflux closed chamber device.
A visible effect can also be proven additionally by standardized, high-resolution photographs using our fully acclimated photo studio and USR-CliP (Unit for Standardized and Reproducible Clinical Photography). If desired, such high resolution photos (50 MPix Hassleblad camera) are of course also suitable for marketing purposes. If only subjective assessments of the product properties by the subjects are desired, lip care products can of course also be evaluated in a simple home-in use study.