Green tea leaves are full of polyphenols, a family of plant compounds that behave as antioxidants. The most abundant and most studied is epigallocatechin gallate, usually shortened to EGCG. In laboratory work EGCG does several things that sound promising for skin: it neutralizes free radicals, it dampens inflammatory signaling, and it interferes with some of the enzymes that break down collagen after UV exposure.
The step that gets glossed over in marketing is how much of that translates to a cream applied to a face. Polyphenols are large, unstable molecules. They oxidize quickly, they penetrate skin unevenly, and the amount of actual EGCG in a product labeled "green tea extract" varies enormously between manufacturers and is almost never stated. Two products with identical ingredient lists can be doing very different amounts.
Where topical green tea holds up best is the soothing effect. Applied to irritated or flushed skin it reduces the look of redness and the feeling of stinging in a way most people can perceive. There is also a reasonable case for its use in oily skin, where it appears to modestly reduce sebum. Claims about wrinkles, firming and pigment are extrapolations from lab work and from oral studies, not from strong topical evidence.
Green tea extract is one of the better tolerated botanicals, but no plant extract is risk-free.
Almost nobody has to avoid topical green tea extract, and that is part of why it appears in so many products.
Avoid it if you have had a contact allergy to it before, or if you patch-test positive to it. If you react to many botanical extracts as a group, look for a plainer formula built on glycerin, ceramides and petrolatum rather than a botanical blend.
Do not use tea compresses or homemade preparations on broken, weeping or eczematous skin.
Caffeine content is worth a sentence, because people ask. Green tea extract contains a small amount of caffeine, and applying it to skin does not deliver a meaningful dose to your body. It will not affect sleep and it does not matter in pregnancy.
Pregnancy and breastfeeding: topical use is fine. Concentrated oral green tea extract supplements are a separate discussion to have with your doctor.
The honest caveat is not about safety but about expectation. If you are buying it for wrinkles or dark spots, the evidence is thin and you will probably be disappointed.
Days one to seven. The soothing effect is the fastest thing to notice. Skin that stings from other products often stops stinging within a few applications, and background redness looks a little calmer.
Two to four weeks. If it is going to help visible redness, this is where you will see it. The change is a softening, not a clearing — the flush looks less angry, not absent.
Six to twelve weeks. Any effect on oiliness shows up slowly and is easy to overstate. Compare photographs rather than impressions if you care.
Pigment and lines: do not set a timeline, because there is no good evidence topical green tea meaningfully changes either. If a product containing it improved your dark spots, look at what else was in the bottle.
When you stop. Redness returns to its baseline over a week or two. There is no rebound and no withdrawal — you simply lose the soothing you were getting.
If four to six weeks pass and reactive, flushing skin is no better, the answer is not a stronger green tea product. It is a diagnosis: rosacea, seborrheic dermatitis and eczema all look like generic redness and all have real treatments.