Camellia sinensis (green tea) leaf extract is a polyphenol-rich botanical standardized for catechins—primarily epigallocatechin-3-gallate (EGCG), plus EGC, ECG, and EC—alongside caffeine, theanine, and minor phenolics. In topical skin care, catechins act as potent redox modulators and anti-inflammatories: they quench ROS, down-regulate NF-κB/COX-2–driven cytokines, and inhibit UV-induced matrix metalloproteinases implicated in photoaging. Formulation-level outcomes include adjunct photoprotection (reduced UV-erythema), visible tone evenness (calmer redness), and anti-aging support via MMP suppression. In oily or acne-prone skin, green tea extracts are often used at 0.2–3% (actives-adjusted) in low-pH aqueous gels, serums, and sunscreens for sebum moderation and post-inflammatory calming. Stability is maximized at mildly acidic pH (~4–6), with chelators and co-antioxidants (e.g., sodium phytate/EDTA; ascorbic acid/ferulic acid) and light/oxygen-protected packaging.

In hair/scalp care, EGCG and related catechins provide scalp antioxidant defense and soothing benefits, targeting oxidative stress and irritation that can impair follicular function. Preclinical and early translational data suggest EGCG may modulate 5-α-reductase signaling and support dermal papilla biology, which is relevant to hair-fiber retention; practically, brands position green tea extract in scalp toners, light conditioners, and leave-on treatments aimed at balancing sebum, reducing odor-causing oxidative by-products, and improving scalp comfort.