Table 2.
Beneficial effects of tea and its active constituents towards the skin-summary.
| Activity | Experimental Model | Type of Tea/Active Constituent | Mechanism of Action/Effect | Reference | |
|---|---|---|---|---|---|
| In vitro | In vivo/Ex vivo | ||||
| Antioxidant | DPPH, ABTS, FRAP assays | Different animal models | Tea catechins (EC, EGCG, EGCG) | • Direct ROS and RNS scavenging • Chelation of trace elements, which are involved in free radicals generation (Cu, Fe) • Increasing of the endogenic antioxidant enzymes production (SOD, glutathione) • Inhibition of enzymes involved in ROS generation (glutathione S-transferase, microsomal monooxygenase, mitochondrial succinoxidase or NADH oxidase) • Protection and regeneration of antioxidant substances (vitamin C or E) |
[5,43,44,47,48] |
| Phase II, clinical evaluation | Topical application of gel containing EGCG | Improvement in skin texture and skin appearance in 45% of volunteers after a 4-week application | [92] | ||
| Double-blinded, placebo-controlled trial 40 women with moderate photoaging 8 weeks of treatment | Green tea extract - oral supplementation (300 mg, 2 per day) - topical application of 10% green tea cream |
- Skin biopsies revealed significant improvement in the elastic tissue content - No clinically significant changes regarding protection from cutaneous signs of photoaging were detected |
[93] | ||
| 24 volunteers | Different cosmetic formulations containing vehicles supplemented with 6% Camellia sinensis glycolic leaf extracts Application to the forearm skin |
- Significant increase in skin moisture (immediate and long-term) - Improved skin microrelief (skin texture) (especially after 15–30 days of treatment) - Significant enhancement of the skin viscoelastic-to-elastic ratio (Uv/Ue; after 30 days) |
[41] | ||
| Photoprotective | Normal fetal lung fibroblasts (MRC5) Adult skin fibroblasts (84BR) Normal human epidermal keratinocytes (NHEK) |
Peripheral blood cells obtained from10 healthy non-smoking volunteers (six female and four men) | EGCG (in vitro assay) 540 mL of green tea infusion (in vivo study) |
- Significant inhibition of UVR-induced damage to peripheral blood cells - Dose-dependent inhibition of the UVR-induced DNA damage in fibroblasts and keratinocytes cell cultures - 250 µM of EGCG was found to be optimal concentration to inhibit DNA cell damage caused by UVR |
[63] |
| 21 voluntary healthy participants Skin patches irradiated with UVB (up to 100 mJ/m2) |
External application of a water in oil emulsion containing 4% of green tea extract | - Significant decrease of UV-induced p53 expression in keratinocytes - Significant reduction of apoptotic keratinocytes - Significant reduction of the UV-induced erythema and thymidine dimer formation |
[72] | ||
| A double-blind placebo-controlled assay - 10 healthy volunteers - skin explants (ex vivo study) |
White and green tea extracts applied topically in a specially prepared cosmetic vehiculum | - Significant reduction of cutaneous immunity in UV-irradiated skin (stronger in the case of green tea) - Prevention of UV-induced oxidative DNA damage in the form of 8-OHdG (8-hydroxy-2′-deoxyguanosine) |
[66] | ||
| 24 male albino hairless mice (HRS/J-hairless, Jackson, Bar Harbor, ME, USA) | Green tea and Ginkgo biloba glycolic extracts Topical formulation containing 6% of each extract applied in two different areas in a concentration of 5 mg/cm², 15 min prior UV irradiation |
- Significant reduction of the UV-induced skin damage (dryness, irritation, presence of erythema, sunburn cell formation and epidermal hyperplasia) - Much stronger effect when both extracts were applied together - Strong photoprotective activity due to biological effects caused in the skin and not photo-absorption properties of both herbal extracts |
[69] | ||
| Anticellulite and slimming properties | More than 24 clinical placebo-controlled trials performed on obese patients | Oral ingestion of 600–900 mg of tea polyphenols per day (equal to 3–4 cups of green tea) |
- Significant reduction of the total abdominal fat - Significant reduction of the weight - Significant reduction of the skin fat tissue - Reduced serum triglycerides - Induced adipogenesis - Increased energy expenditure–increased fat oxidation - Improved fecal lipid excretion |
[5,82,83,84] | |
| Swine hypodermis | Caffeine Three models: - Gel with ultrasound treatment (3 MHz, intensity: 0.2 W/cm2, rate: 1 min/cm2), - Gel with caffeine (5%, water-in-water) - Gel with caffeine and ultrasound Application during 15 days |
- Model using caffeine and ultrasound was proved to be the most effective - Significant reduction of the subcutaneous adipose tissue, damage of the adipocytes and the numbers of cells |
[79] | ||
| Wistar female mice | Cosmetic emulsion containing 4% of caffeine applied topically for 21 days | - Significant reduction (by 17%) of the fatty cells diameter | [80] | ||
| Clinical study - 15 healthy female volunteers with cellulite on the thigh and medial side of the upper arms |
Slimming cream containing 3.5% of water-soluble caffeine and xanthenes for the treatment of cellulite Topical application twice daily for 6 weeks |
- Significant improvement in skin condition - Significant reduction of the cellulite (by 19.8%) - Reduction of thigh (0.7 cm-1.7%) and upper arm (0.8 cm-2.3%) circumferences - No side effects |
[81] | ||
| Double-blinded, randomized trial 20 women with a moderate degree of cellulite 4-week treatment |
Anti-cellulite cream containing black pepper, sweet orange peel, ginger root extract, cinnamon bark extract, capsaicin, green tea and caffeine. Topical application Combination of anti-cellulite cream and occlusive bioceramic-coated neoprene garment |
- 76% volunteers reported improvement of their cellulite - 54% women declared greater improvement in the thigh that received garment occlusion - Significant improvement of the skin of the thighs condition (average circumference reduction was 1.2 cm; 1.3 cm in the group with oclussion and a 1.1 cm reduction without occlusion) |
[87] | ||
| 29 women aged 25–48 with a cellulite grade 2 according to the Nurnberger–Muller scale | Dietary supplementation with chokeberry juice rich in polyphenols 100 mL/day for 90 days |
- Significant reduction in the subcutaneous tissue thickness (1.9 mm on average) - Length of subcutaneous tissue fascicles was reduced in 97% of subjects - Reduction of edema in 55.2% of patients after 45 days of treatment - Lack of edema in all subjects after 90 days of treatment - No qualitative or quantitative determinations of the phenolic composition of the juices were performed |
[90] | ||
| Improvement of skin and hair condition | Clinical double-blind placebo study 36 participants (18 in the study group and 18 in the placebo group) |
Dietary supplement containing 300 mg of green tea extract (twice daily) and topical application of a green tea cream (10%)—two times per day, for 8 weeks | - No statistical changes of the skin of the patients from both groups (dermatological examination) - Skin biopsy revealed significant improvement in elastic tissue content in the green tea treated group |
[93] | |
| Randomized single-blind, placebo-controlled study 20 healthy Thai volunteers (16 female and 4 male) aged between 20 and 35 years old |
Cosmetics preparation, which contained 2%, 4.5% and 7% of green tea extract with 100 mg% of polyphenols (the base consisted of hydroxyethyl cellulose, glycerin and panthenol). Topical application for 28 days. |
- Significant anti-greasy and anti-sebum activity of a green tea extract - High efficiency in the improvement of oil face condition - The activity was highly correlated with the concentration of green tea extract - The effectiveness of a 28 days treatment was significantly better than 14 days - Patch testes revealed no irritation properties |
[94] | ||
| Single-blinded, placebo controlled monocentric study 22 non-smoker, healthy men |
Cosmetic preparation containing lotus and green tea extract. Application on cheek at bedtime for 60 days. Sebum production was evaluated at baseline and after 15, 30, 45 and 60 days. |
- Significant reduction of sebum production - Higher efficacy in the group applying only green tea, compared to a combination of green tea and lotus (not statistically significant) - The highest effectiveness was achieved after 60 days of treatment |
[95] | ||
| Clinical investigation-10 healthy men aged 24–40 years | Cosmetic formulation containing 3% of green tea extract applied to the cheeks for 8 weeks. | - Significant decrease in sebum production - The highest efficiency was achieved after 8 weeks of treatment (60% of sebum reduction) - Significant improvement already after 1 week of treatment (sebum production decreased by 10%) |
[97] | ||
| Hair follicles from 14 biopsies, taken from the vertex areas from male with androgenic alopecia | Caffeine External application of caffeine in a concentration of 0.001 and 0.005% |
- Significant stimulation of hair follicle growth - Reduction of a smooth muscle tension near the hair follicle - Significant increase of the nutrients delivery to a hair papillae |
[98] | ||
| Placebo controlled study 30 mice |
Animals were fed with a diet enriched with 50% fraction of polyphenol extract from dehydrated green tea in their drinking water for six months | - Significant improvement in hair growth (33% of animals) in comparison to control group | [99] | ||
| Cultured human dermal papilla cells | Hair follicles ex vivo culture Three normal human volunteers |
EGCG 0.01, 0.1 or 0.5 μM (in vitro) 0.1, 1 or 5 μM (ex vivo) 10% in ethanol or ethanol vehicle (in vivo) |
- Stimulation of the culture cells growth - Proliferative and anti-apoptotic effect towards dermal papillae of human scalps - Prolongation of anagen stage |
[102] | |
| Improvement of skin microcirculation | Double-blind, placebo-controlled study 60 female volunteers |
Green tea beverage (1402 mg of catechins per day) for 12 weeks. | - Significant improvement in blood flow (40% by week 6 and 29% by week 12) - Significant improvement in oxygen delivery to the skin (from 30% at the baseline up to 38% and 40% by week 6 and 12, respectively) - Significant improvement of several skin parameters (elasticity, roughness, scaling, density and water homeostasis) |
[5] | |
| Randomized, double-blind, single-dose study 15 female volunteers |
Green tea extract (0.5, 1.0 and 2.0 g) administrated orally in a form of capsule | - Maximized blood flow 30 min. after ingestion - Significant improvement of skin condition - Increased blood flow and microcirculation in the skin tissue |
[5] | ||
| Clinical investigation in a group of 20 volunteers (nine men and 11 women) with wounds | Topical application of antiseptic agent containing tee tree oil (5% in a saline) | - Significant increase (+19%) of blood flow compared to control - Significant improvement of wound healing (in comparison to ocetnidine and polyhexanide) - Alterations in the hemoglobin oxygenation (not significant) - Significant improvement of skin perfusion - Strong antibacterial activity |
[103] | ||
| Clinical investigation in a group of 134 women with cellulite, aged between 20–39 years | Commercially available cosmetic (Elancyl® Chrono-Active) containing 7% of caffeine Topical application for 1 month |
- Insignificant improvement of skin microcirculation (functional capillary density, number of flowing capillaries per unit area, diameter of the dermic papilla and capillary diameter) - Significant reduction of thigh and hip circumferences in 80% and 67% of cases, respectively - No influence of alcohol consumption, tobacco smoking and level of physical activity on thigh and hip circuit was revealed |
[107] | ||