Epigallocatechin Gallate

Epigallocatechin gallate — almost always shortened to EGCG, and sometimes written epigallocatechin-3-gallate — is a plant polyphenol belonging to a family of compounds called catechins. It is the most abundant catechin in the leaves of Camellia sinensis, the plant that gives us green tea, and it is responsible for much of the interest cosmetic chemists have taken in green tea over the past three decades.

In skincare you will meet it in two guises. Occasionally it appears as a purified, isolated ingredient, which allows a formula to state a specific percentage. Far more often it arrives inside a broader green tea extract, sitting alongside other catechins, caffeine and amino acids — in that case the ingredients list will read Camellia Sinensis Leaf Extract rather than EGCG, and the catechin content is rarely disclosed.

It is used first and foremost as an antioxidant, and turns up in serums, essences, lightweight moisturisers, eye creams, sheet masks and after-sun products. Where a purified form is used it is most often around 1% or below, though a small number of formulas go higher; it is at those higher levels that its reputation for helping to keep shine in check comes from.

One honest caveat: much of the famous EGCG research concerns green tea drunk or taken orally rather than applied to skin. Topical work in people does exist, but the trials are comparatively small and few in number, so EGCG is best described as a very well-characterised molecule with a promising, still-developing topical evidence base.

EGCG is built around several phenol rings carrying an unusually high number of hydroxyl groups. Those groups give up hydrogen atoms very readily, and that is the whole chemical basis of antioxidant behaviour: when an unstable free radical forms in the surface layers of skin, EGCG can hand over a hydrogen and quench it, ending up as a comparatively placid molecule itself instead of letting a chain reaction run on. It can also bind loose metal ions that would otherwise help drive those reactions along.

Radicals of this kind are produced on skin every day by UV, pollution and the ordinary oxidation of sebum on the surface. Researchers link that background oxidative stress to the visible signs of ageing, which is why antioxidants are positioned as a daily buffer rather than a corrective step.

Two practical consequences follow from the same chemistry. Because EGCG parts with electrons so willingly, it is inherently unstable: it oxidises on exposure to air, light, heat and alkaline conditions, browning as it goes, which is why formulas keep it on the acidic side and reach for chelators and airless packaging. And because it is a large, water-loving molecule, it does not cross the skin barrier easily, which is why so much laboratory work has gone into delivery systems such as liposomes and nanoparticles.

EGCG is an everyday antioxidant rather than an active you need to build up to slowly.

• Morning makes most sense. Antioxidants earn their keep ahead of a day of UV and pollution, so apply to clean skin before your moisturiser. Twice daily is fine if the texture suits you.
• It partners sunscreen, it does not replace it. EGCG filters nothing. Keep using a broad-spectrum SPF 30 or higher.
• Judge the packaging. Opaque tubes, pumps and airless bottles protect it far better than clear jars or wide-necked pots.
• Watch the colour. A formula that has turned deep amber or brown and smells stale has oxidised — replace it rather than finishing it.
• Know the numbers. Purified EGCG is usually listed at 1% or less, and higher-strength formulas are unusual; whole green tea extracts will not tell you at all, so judge them on how your skin responds.
• Layer freely. It sits comfortably with niacinamide, hyaluronic acid, peptides and the classic vitamin C and E pairing. If you also use retinoids or exfoliating acids, alternate evenings rather than piling everything on at once.