EGCG: sebum went down — but every arm went down, and none got the plain base

A 2013 paper from Seoul National University, in the Journal of Investigative Dermatology — a weighty place in this field.

Most of the paper is laboratory work. EGCG was applied to a human sebocyte line (SEB-1) to see what happened.

• Reduced sebum production — via the AMPK-SREBP-1 signalling pathway
• Reduced inflammation — by suppressing the NF-κB and AP-1 pathways
• Killed sebocytes themselves — by inducing apoptosis
• Decreased the viability of the acne bacterium (P. acnes)

The authors' phrasing was that EGCG targets almost all the pathogenic features of acne. As laboratory work it is tight.

And at the end there is a human trial.

EGCG significantly improved acne in an 8-week randomised, split-face clinical trial, and was well tolerated.

That is everything the abstract says.

• No participant count
• No statement of what the control was — vehicle, or another ingredient
• No concentration
• No number for the size of the improvement

We left those fields blank. What is established is the split-face design, the eight weeks, and that it was significant.

Why this sits at 'moderate'. There is a randomised split-face human trial, the journal is solid, and the laboratory mechanism lines up with the clinical result. But without knowing the size or the comparator, it cannot go higher.

It is this site's rule that laboratory work, however tight, does not raise a grade by itself. The PLLA and exosome pages draw the same distinction — what changed in tissue or cells and what shows in the mirror are different questions.

A 2023 randomised clinical trial in Thailand, in people with seborrhea — faces that turn greasy because they produce a lot of sebum.

Ninety people were split into three arms and applied cream for four weeks. All three creams were built on the same dimethicone and glycerin moisturising base, with an active added.

• 2% l-carnitine
• 5% EGCG
• 2% l-carnitine + 5% EGCG

Sebum level, stratum corneum capacitance and transepidermal water loss (TEWL) were measured at weeks 0, 1, 2 and 4, and quality of life and subjective outcomes were assessed.

The results.

• Sebum fell significantly from baseline in all three arms (P < .01)
• The median time to oil control was longer in the l-carnitine arm
• The combination arm was significantly better than l-carnitine alone (P = .009)
• The other objective parameters and subjective outcomes improved significantly in all three

What is valuable here is the endpoint. Sebum comes out as a number on a sebumeter — not someone reporting that it feels less greasy, but an instrument reading. The condition we keep wishing for in this site's procedures layer is met here.

And that the combination beat l-carnitine alone means that what was added actually did something. The kojic acid page records an add-on comparison of the same shape.

But the abstract gives no comparison between the EGCG-alone arm and the combination. The only significant pair reported is combination against l-carnitine. Whether that is the gain from adding EGCG, or the gain from stacking two things, this one line cannot settle.

And four weeks is short.

This is the biggest hole in the trial above.

What the three arms received was a moisturising cream with an active in it, in every case. There was no arm applying the base with no active at all.

Why that matters.

The cream base is dimethicone and glycerin. Both do something to skin on their own — dimethicone films the surface, and glycerin holds water. On top of that, the act of applying a moisturising cream is itself a matter of wiping off surface oil and covering it again.

So 'sebum fell significantly in all three arms' cannot distinguish between:

1. The actives reduced sebum production
2. The base alone would have reduced it as much
3. It fell because season, humidity and daily life changed over four weeks

The lactic acid page on this site has a 1983 trial that handled exactly this problem. There, a plain emollient was included as a comparator, and all three arms significantly improved xerosis. What the ingredient contributed only emerged after treatment stopped.

So this item is filed as 'not established'. What is not established is whether EGCG itself contributes beyond the base.

Separating what is and is not established:

• Sebum fell — established (instrument-measured)
• The combination beat l-carnitine alone — established
• Whether EGCG beats a cream with nothing in it — not established