All true teas are derived from Camellia sinensis. Black tea is the most processed (fermented) with white tea recently supplanting green tea as the least processed; oolong is partially fermented. Green tea contains 8-12% polyphenols and 2-4% caffeine (10-80 mg/cup). White tea is a more potent antioxidant and more effective than green tea in inhibiting bacterial dysplastic mutations (3,22,56). Green tea decreases melanoma cells in tissue culture and squamous cell carcinoma cell formation with topical and oral administration in mice. It also increases keratinocyte cell differentiation improving wound healing. This tea inhibits Streptococcus species and Escherichia coli. It also inhibits bradykinin and prostaglandins in animals (57). Black tea has a much lower content of catechins than green tea, but a higher content of other flavonoids such as kaempferol and theaflavin. The largest catechin and most active antioxidant in any tea is epigallocatechin gallate (EGCG). Green tea has the highest concentration of EGCG (3).
Topical green tea provided photoprotection beginning at 24 hours and lasting 48-72 hours. It reduced the number of sunburn cells by 66% when applied 30 minutes prior to UVB. When applied at 1-10% concentrations, a dose response inhibition of UV-induced erythema occurred (58). This extract prevented psoralen UVA photodamage with pre – and post-treatment by reducing erythema, hyperplasia, and hyperkeratosis (59,60). Green tea is used to soothe sunburn, reduce baggy eyelids, reduce gingivitis and produce hemostasis and prevent UV induced carcinogenesis including oral leukoplekis (2,22). Black tea extracts applied pre – and post-ultraviolet light challenge decreased signs of cutaneous photodamage, carcinogenesis, and inflammation in human and mouse skin (22). Oral administration of black and oolong
teas, like green tea, suppressed both type I and IV allergic reactions in the skin (61). Oral oolong tea effectively treated atopic dermatitis (62).
A recent double-blinded trial of 51 patients treated for 12 weeks with topical green tea extract containing 5.5-8.5% EGCG did not reduce the number of actinic keratoses on forearms compared to placebo (63).
The major adverse reactions are gastrointestinal upset, constipation, irritability, and very rare hepatotoxicity, delirium, and seizures. Caution should be used during pregnancy and lactation with excessive consumption (>3 cups or 300 mg per day) (22).