JOURNAL OF COSMETIC SCIENCE 84 DISCUSSION Interesting effects of the cosmetic product in patients with sensitive skin were observed: a preventive soothing effect, an immediate soothing effect, and a soothing effect on ery- thema. SLS and capsaicin tests confi rmed these data. A favorable effect on quality of life was also noted. The product was appreciated by volunteers for its effi cacy, tolerance, and cosmetic qualities. These results were obtained in two different countries: France and Thailand. Although the pathophysiology of sensitive skin remains unclear (22), the underlying mechanism is not immunological or allergic. There are not usually any histological ab- normalities. Skin barrier function is altered in many patients, which may promote con- tact with triggering factors (23). Skin sensitivity may also cause dryness. Skin dryness and skin sensitivity could also be consequences of the same pathogenic mechanism when the two conditions are associated. Regular use of skin moisturizers seems to improve skin sensitivity (24). The role of “keratinocytic infl ammation” is possible when cytokines are released. Abnormal sensations and vasodilatation strongly suggest the cutaneous nervous system’s involvement (22). Neurotransmitters (25) may induce neurogenic infl ammation after being released, when transient receptor potential (TRP) channels are activated (7). The main TRP is TRPV1, which is expressed by nerve endings and keratinocytes in the skin. Sensitive skin seems to be the result of a vicious cycle between neurogenic and “ke- ratinocytic infl ammation,” with the release of neurotransmitters and cytokines. Rhamnose is a monosaccharide which was previously known to decrease IL-8 secretion by inhibiting the interactions of T-cells with keratinocytes through intercellular adhesion molecule 1 (26). Mannitol and xylitol are polyols. Mannitol is also a hydroxyradical scav- enger, which affects keratinocytes, for example, by inhibiting UV B–induced oxidative Figure 4. Immediate soothing effect on Asian skin. Figure 5. SLS test after 24 h: Patient number 7.

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