SKIN CARE Product applications Day
Pre-application protection
TEWL & erythema Assessment Figure 8: Protective action - clinical protocol.
Skin barrier function & irritation evaluation upon surfactants exposure The study aimed to evaluate the protective and repairing effect of a cream cosmetic product, containing the lipophilic active, against the skin alterations caused by sodium lauryl sulfate (SLS), a typical irritant agent contained in personal cleansing products. The skin was exposed to a solution at 2% SLS, using Finn chambers, for a period of 24 hours. Two different protocols were followed: a
preventive one, in which a cream formulation containing 2% lipophilic active was applied prior to the stress (protective effect), and a therapeutic one, in which the product was applied after exposure to SLS (repair action). Skin barrier function, evaluated by the measurement of the TEWL (Tewameter 300®) and skin irritation, evaluated by the measurement of skin erythema (Mexameter® MX 18, Courage+Khazaka, Electronic), were assessed on a group of ten healthy volunteers.
Protective effect: Clinical protocol In the protective protocol (Figure 8), the effect of cosmetic topical product application prior to the skin’s exposure to SLS was evaluated. Selected skin areas were kept untreated as controls. Other skin areas were treated with a placebo or the same formulation containing 2% lipophilic active (2 mg/cm2
) for a period of ten days, preceding exposure to the chemical agent.
Product applied after SLS exposure -Post-treatment
0 -5
-10 -15
-20 -25 -30 -35 -40
On Day 11, a solution of SLS was applied
to all the skin areas, using Finn chambers to chemically aggress the skin. The Finn chambers were kept in contact with the skin for 20±4 hours and removed on Day 12. TEWL and skin erythema were assessed and the obtained values were set as the baseline for skin barrier disruption (high TEWL values) and skin irritation (high level of erythema), respectively. The extent of barrier repair and the disappearance of erythema were measured at intervals of 30 minutes, one hour, two hours and 24 hours after removal of the SLS patch. Parametric data were submitted to a two-way paired Student’s t-test. The results showed that the skin’s exposure
to SLS compromised the barrier function. Untreated skin progressively repaired itself. The placebo treatment did not affect the barrier repair compared to the untreated skin. Protecting the skin with the lipophilic active formulation allowed a faster barrier recovery, as shown by the reduction of the SLS-induced TEWL (-15.5%, -29.3%, -33.0% and -37.1% after 30 minutes, one hour, two hours and 24 hours from patch removal, respectively, Figure 9). The measurement of skin erythema also
showed that the application of the lipophilic active formulation protects the skin from chemically induced erythema. Exposure to SLS caused clinical signs of skin irritation. An elevated level of erythema persisted on untreated skin for up to 24 hours
Untreated skin ■ Placebo ■ Lipophilic active ■
Product applied after SLS exposure -Post-treatment
6 3 0
-3 -6 -9
30’ 1h 2h Time after SLS-patch removal Figure 9: Variation in TEWL in the protective protocol
www.personalcaremagazine.com 24h
-12 -15 -18
after SLS exposure. The preventive application of the lipophilic active formulation showed a faster disappearance of skin irritation (a reduction in erythema of -7.7%, -9.5%, -12.2% and -15.6% after 30 minutes, one hour, two hours and 24 hours from patch removal, respectively) compared to the application of the placebo (Figure 10).
Repairing action – clinical protocol In the repairing protocol (Figure 11), the restoring and soothing action of the lipophilic active versus the damage caused by surfactants was evaluated. Some skin areas were treated with cosmetic topical products only upon removal of the Finn chambers containing SLS (Day 12). Selected skin areas were kept untreated as controls. In this case, the skin was post-treated with one single application (2 mg/cm2
) of a
placebo or the same formulation containing 2% lipophilic active. The repairing effect of the treatments was assessed for skin barrier function and skin irritation at intervals of 30 minutes, one hour, two hours and 24 hours from the topical application of the formulations. The skin barrier function and irritation were assessed as described above. Parametric data were submitted using a two- way paired Student’s t-test. Results obtained in the repairing
experiment revealed that applying the lipophilic active formulation after the
Untreated skin ■ Placebo ■ Lipophilic active ■ Baseline Effect of pre-treatment 0 1 10 11
2% SLS (Finn Chamber, 24hrs) 12
87
13 30’ 1h 2h 24h
30’
1h
2h Time after SLS-patch removal Figure 10: Variation in skin erythema in the protective protocol November 2021 PERSONAL CARE
24h
% variation in TEWL Protective effect
% variation in skin erythema Protective effect
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