In 2011, Choi and Kim assessed the whitening effect of black tea water extract topically applied twice daily (6 days a week for 4 weeks) to UVB-induced hyperpigmented spots on the backs of brown guinea pigs. Treatment was divided into control (UVB and saline), vehicle control (UVB, propylene glycol, ethanol, and water), positive control (UVB and 2% hydroquinone), and two experimental groups (UVB and 1% black tea; UVB and 2% black tea). The investigators observed that the hyperpigmented spots treated with hydroquinone and black tea were clearly lighter than those treated by the control or vehicle-control groups. Histologic examination revealed that melanin pigmentation, melanocyte proliferation, and melanin production were significantly diminished in the groups treated with hydroquinone and both concentrations of black tea. The authors concluded that black tea suppresses melanocyte proliferation and melanosome synthesis in vivo, thus displaying the capacity to whiten skin in brown guinea pigs.16
In 2013, Yeh et al. found in nude mouse skin in vitro that niosomes appear to be feasible as a delivery vehicle for the dermal administration of black tea extracts as a sunscreen agent.1
Topical studies in humans
Building on findings 3 years earlier18, Türkoglu et al., in 2010, assessed the photoprotective effects of dermal gels produced from green and black tea aqueous extracts tested in vivo in the forearms of six volunteers exposed to artificial UV light (200-400 nm). In addition to the green tea and black tea gels, a 0.3% caffeine gel, a carbomer gel base, and a control were tested. The investigators reported no eruptions of UV-induced erythema in any of the black and green tea gel sites, but erythema was present to varying degrees at the areas treated with caffeine gel, carbomer gel, and control. The investigators concluded that the black and green tea extracts exhibited potent UV absorbance and that the formulated gels were effective in protecting the skin against UV-induced erythema. Further, the investigators suggested that these agents have the potential to protect against other harm caused by UV radiation, including photoaging.19
Conclusion
Though not as widely investigated as green tea, the therapeutic potential of black tea is of great interest. Although an abundance of laboratory evidence has emerged, clinical evidence is sparse. Nevertheless, laboratory data suggest the potential uses of black tea in the dermatologic realm and justify more human trials.
References
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Dr. Baumann is chief executive officer of the Baumann Cosmetic & Research Institute in the Design District in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote the textbook “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002) and a book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). She has contributed to the Cosmeceutical Critique column in Dermatology News since January 2001. Her latest book, “Cosmeceuticals and Cosmetic Ingredients,” was published in November 2014. Dr. Baumann has received funding for clinical grants from Allergan, Aveeno, Avon Products, Evolus, Galderma, GlaxoSmithKline, Kythera Biopharmaceuticals, Mary Kay, Medicis Pharmaceuticals, Neutrogena, Philosophy, Topix Pharmaceuticals, and Unilever.