The Journal of Photochemistry and Photobiology (December 31, 2001) stated that the polyphenols “are the active ingredients in green tea and possess antioxidant, anti-inflammatory and anticarcinogenic properties. Studies conducted by our group on human skin have demonstrated that green tea polyphenols (GTP) prevent ultraviolet (UV)-B…-induced immune suppression and skin cancer induction.” Because of this, when combined with traditional sunscreens, green tea polyphenols may have an additive or synergistic photoprotective effect.

Most researchers agree that tea (black, green, or white) has potent anti-inflammatory properties and that it is a potent antioxidant whether consumed orally or applied topically. Current research also indicates that epigallocatechin-3-gallate (EGCG), an extract of tea, can prevent collagen breakdown and reduce UV damage to skin, which is a very good reason to use skin-care products that contain one or more forms of tea.

But which tea extract is the best? Green, white, black or red?

Natural flavonoids, such as green or black tea polyphenols have been show to reduce UVB-induced erythema, tumorigenesis, and immunosuppression in mice.

White tea appears to be a more potent antioxidant than green tea.

Black tea has a much lower content of catechins than green tea, but a higher content of other flavonoids, such as quercetin, theaflavin, and kaempferol. Black tea extracts applied before and after UV light challenge have been shown to decrease signs of cutaneous photodamage, carcinogenesis, and inflammation in human and mouse skin.

Most cosmeceutical products containing tea extracts or phenols have not been tested in controlled clinical trials, but these substances have shown compelling evidence for antioxidant, anti-inflammatory, and anticarcinogenic activities. Unfortunately, the concentration of phenols is not standardized in skincare products containing green tea; therefore, some products may have little-to-no therapeutic effect, making purchasing them a challenge for consumers. It is generally accepted that five-percent green tea extract or polyphenols in the 90-percent range is an effective concentration.

See also kombucha and photostabilizers.

Sources
Cosmetic Dermatology, October 2010, pages 446-449
Archives of Dermatological Research, March 2010, pages 71–83
Skin Pharmacology and Physiology, September 2009, pages 299–304
Skin Research and Technology, August 2009, pages 338–345
Dermatologic Surgery, July 2009, pages 1,057–1,065
Experimental Dermatology, June 2009, pages 522–526
Food and Chemical Toxicology, April 2008, pages 1,298–1,307
Photodermatology, Photoimmunology, and Photomedicine, February 2007, pages 48–56
Journal of Dermatological Science, December 2005, pages 195–204
Skin Pharmacology and Applied Skin Physiology, 2001, pages 69–76
Practical Uses of Botanicals in Skin Care in the Journal of Clinical Aesthetic Dermatology 2009 Jan; 2(1): 36–40.