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SKIN CARE
Neuronal hyper-reactivity
= excessive response of nerve endings
Hyperstimulation
of nociceptors, including TRPV1 which is the reference receptor
Figure 2: Infernal trio of sensitive skin
Treating a co-culture of keratinocytes and sensory neurons with capsaicin causes a significant calcium entry in neurons, reflecting the activation of the receptor TRPV1. Tested at 0.25%, Salvia miltiorhizza active significantly inhibits the activation of the sensitive skin receptor TRPV1 by 115%, thereby limiting neuronal hyper-reactivity of the skin.
2. Restoring skin barrier quality A large number of studies have suggested that skin sensitivity is related to an alteration of the barrier function and this change is the origin of a sensation of discomfort.2
Damage to the skin
barrier leads to various consequences. First, trans-epidermal water loss (TEWL)
is increased, which explains the sensation of dryness felt by individuals susceptible to cutaneous hypersensitivity.3,7,8,9
The exposure
of sensory neurons is also augmented, which thus exacerbates sensorial perceptions.10 Finally, it facilitates the penetration of irritant and allergenic substances responsible for inflammation characterized by the production of cytokines, leukotrienes and prostaglandins (Figure 3).1,2,3 Preserving the barrier function is therefore
important in determining the comfort provided by a skin care product. Thanks to Salvia miltiorhizza active tested at 2.5% on sensitive Caucasian skin, TEWL in the face and hands
1 Increase of TEWL ➡ Dryness/discomfort
is significantly reduced by 9.6% and 9.2% and hydration of the face and hands is significantly boosted by 13.2% and 10.3%.
3. Reducing skin inflammation Neuronal hyper-reactivity and alteration of the barrier function trigger pro-inflammatory processes. At the level of sensory neurons,
neuromediators secreted in response to the stimulation of TRPV1 activate keratinocytes in proximity to nerve endings.2,6,10
Binding to their
specific receptors leads to the synthesis of pro-inflammatory substances such as cyclooxygenase 2 (COX-2), prostaglandin E2 (PGE2) and leukotrienes B4 (LTB4). In addition, following alteration of the barrier function, the penetration of irritant and allergenic substances causes an inflammation characterised by the production of cytokines, prostaglandins and leukotrienes.3 Controlling the phenomenon of inflammation is
therefore the last cornerstone of effective care for sensitive skin as it causes itching and redness. A novel modelling in vitro has shown that exposure of keratinocytes to particulate matter from pollution, called particulate matter (PM), causes a significant increase of the secretion of COX-2 and PGE2. Treatment with a TRPV1 antagonist significantly reduces the production of COX-2 and PGE2, showing that inflammation caused by PM is
2 Penetration of allergenic & irritant substances into the skin
➡ Activation of an inflammatory process (leukotrienes and prostaglandins)
partly due to the activation of TRPV1. Tested at 0.05%, the Salvia miltiorrhiza
active significantly inhibits the secretion of PGE2 by keratinocytes by 95% following treatment with PM. Tested at 0.25% on Silabskin® RE (reconstructed epidermis) subjected to a pollutant stress, it also significantly reduces the synthesis of COX-2 by 34%. Thanks to a novel approach using images
acquisition with an in vivo confocal laser microscope (Vivascope®) which were then quantified by experts on scoring scales, Silab demonstrated that its Salvia miltiorrhiza active significantly limits the inflammatory response of the skin to aggression with LTB4 by 404%. This natural active ingredient therefore targets
the infernal trio of sensitive skin, thereby assisting in its fight against everyday harmful stimuli.
A global solution taking environment and ethnicity into account At the present time, most treatments focus on the issues of skin sensitivity to chemical aggressions but do not really take the lifestyle, environment or ethnicity of consumers into account. These parameters however considerably contribute to the onset of sensitive skin symptoms. Indeed, among environmental factors, cold and pollution are part of the major stressors with the most impact on sensitive skin3
since they
disrupt the skin’s equilibrium by acting directly 3
Increase of exposure nerve endings
➡ Neuronal hyper-reactivity
Altered barrier function
Modification of the lipid
organisation & keratinocytes behaviour
Exacerbated inflammation
Excess production of pro-inflammatory substance Skin sensitivity - Appearance of unpleasant sensations
Figure 3: Barrier function alteration and consequences PERSONAL CARE October 2021
www.personalcaremagazine.com
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