Houttuynia Cordata / Eo-seong-cho / Fish Mint
An extract of Houttuynia cordata, a herb long used in East Asian medicine and now a staple of Korean 'cica-adjacent' soothing products. It's rich in flavonoids (notably quercetin and its glycosides) with antioxidant and anti-inflammatory activity, and it's typically chosen to calm visible redness, reactive skin and breakout-prone congestion. Most of the evidence is pre-clinical or traditional rather than from large topical trials, so treat it as a gentle soothing support rather than a treatment-strength active.
Products often headline a big number — '77% heartleaf', say — but that figure is usually the heartleaf water or extract content, which is mostly water, not a measure of active flavonoid dose. A high percentage of a dilute extract can still be mild. Judge it on where it sits in the ingredient list and the formula overall, not the marketing percentage alone.
Use in a toner, essence or serum after cleansing, AM and/or PM. It's genuinely gentle, so it suits sensitive, redness-prone and acne-prone skin and layers well with almost anything. Think of it as a soothing companion to your actives, not a replacement for them.
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