78
ANTI-IRRITATION
signaling pathway, but 1% extract inhibited their expression by 60% and 49%, respectively. TNF-a promoted IL-6, IL-8, and TNF-a expression, which were inhibited by 56%, 70%, and 48% with 1% rambutan peel extract. UV-induced IL-6 and TNF-a were inhibited
by 15% and 25%, respectively. SLS, which triggers IL-1a expression through an immediate response, was inhibited by 54% with 1% rambutan peel extract (Figure 4).
Scalp irritation-soothing effect A clinical study was conducted to evaluate the irritation-soothing effect on the scalp, which is susceptible to irritation from UV, SLS, and other factors. Twenty subjects aged 21–56 with sensitive
scalps (a* value >5) applied a serum containing 2% rambutan peel extract to the scalp 2–3 times daily for two weeks. Subjects were divided into two groups (rambutan peel extract serum, placebo serum). After a single application, scalp temperature
decreased by about 7% in the rambutan peel extract group compared to placebo group, and by 5% after two weeks of continued use. Scalp erythema and desquamation index also decreased by 37% and 28%, respectively, after two weeks, confirming the scalp irritation-soothing efficacy of the rambutan peel extract (Figure 5).
SLS-induced irritation-relieving effect (immediate relief) A clinical study was conducted to evaluate the effect against SLS-induced irritation, a lifestyle factor. Twenty-one female subjects aged 26–53 applied 1.5% SLS solution on the inner forearm to induce irritation, then applied serums containing 0.5%, 1%, or 2% rambutan peel extract twice daily for two weeks. Untreated and placebo groups without
rambutan peel extract were used as controls. SLS-induced skin irritation was improved in a dose-dependent manner, with 2% extract serum reducing erythema by 24% and TEWL by 50% after two weeks, indicating enhanced skin barrier function (Figure 6). Since SLS induces immediate IL-1a expression,
another clinical study was conducted to evaluate Before
After 1 application Irritant: UV
800 600 400 200 0
Control
400 300 200 100 0
Control UVB 0.5% 1%
Rambutan peel extract
400 300 200 100 0
Control TNF-a 0.5% 1%
Rambutan peel extract
0 Control Figure 4: Inflammatory inhibition effect against LPS, TNF-a, UV, and SLS
immediate soothing effect. Twenty-four female subjects aged 39–60 received 2% SLS on the inner forearm, followed by a single application of o/w emulsion containing 2% rambutan peel extract. Erythema and TEWL were measured within
five minutes. Compared to placebo, erythema was reduced by 18% and TEWL by 27%, demonstrating the rambutan peel extract’s efficacy against immediate SLS-induced irritation (Figure 7).
UV-induced irritation-soothing effect A clinical study was conducted to evaluate the effect against UV-induced irritation. Twenty female subjects aged 23–56 received 2MED UV on the inner forearm, followed by twice-daily application
Before
After 2 weeks
21 * p<0.05 vs. 0 days 18 15 * 12 9 * 2.0% 6 0 Day High temp. Low temp. Figure 5: Soothing effect of rambutan peel extract on sensitive scalp PERSONAL CARE MAGAZINE May 2026
Figure 6: Soothing effect of rambutan peel extract against SLS-induced irritation
www.personalcaremagazine.com 3 Day 14 Day * *
* *
0.5% 1.0%
* * Not application ■ Placebo ■
O/W emulsion with Rambutan peel extract ■ Erythema Index (E.I.)
270 * p<0.05 vs. 0 days 240 210 * 180 150 120 0 Day 3 Day TEWL 14 Day
* *
*0.5% 1.0%
* *
2.0% SLS 0.5% 1%
Rambutan peel extract
UVB 0.5% 1%
Rambutan peel extract
400 300 200 100 0
Control TNF-a 0.5% 1%
Rambutan peel extract
300 200 200 100 0 Control TNF-a 0.5% 1%
Rambutan peel extract
100 Irritant: TNF-a Irritant: LPS
0 Control LPS 0.5% 1%
Rambutan peel extract
200
100
0 Control LPS 0.5% 1%
Rambutan peel extract
Irritant: SLS 200
100
Placebo serum
(With 2% Rambutan peel extract) Scalp serum
Placebo serum
(With 2% Rambutan peel extract) Scalp serum TNF-a mRNA level (%) IL-6 mRNA level (%)
TNF-a mRNA level (%)
IL-8 mRNA level (%)
IL-6 mRNA level (%)
TEWL (g/m2
h)
Erthema Index (E.I.)
IL-1a mRNA level (%)
IL-8 mRNA level (%)
IL-6 mRNA level (%)
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