A glossary of scalp care botanicals, graded by evidence

Every scalp product has a list of botanicals on the back and a list of promises on the front, and the distance between them is where this category makes its money. This glossary covers twelve botanicals that appear across Korean and Western scalp care, including all twelve in our own bar. Each entry says what the ingredient plausibly does in a rinse-off cleanser, what the most cited evidence actually measured, and gives a grade.

The grading is deliberately harsh, because the category's grading is deliberately generous. It applies to the evidence for a rinse-off scalp product, which is the form most people encounter these ingredients in.

Centella asiatica (병풀, gotu kola, cica)

A herb whose triterpenes (asiaticoside, madecassoside) have a substantial literature in wound healing and skin barrier repair. A 2021 review summarised anti-inflammatory and barrier-supporting effects in skin, mostly from leave-on applications and cell studies. On the scalp, the plausible role is soothing an irritated surface. There is no hair-count study.

Grade: B for soothing skin. D for hair growth.

Red ginseng (홍삼)

Fermentation converts ginseng's ginsenosides into smaller compounds such as compound K, and this is the basis of the fermented-ginseng-for-hair claim. The frequently cited absorption data is from oral dosing in humans, which says nothing about a rinse-off product. Cell studies show ginsenosides affecting dermal papilla cells. In a cleanser, ginseng is a mild stimulant with antioxidant constituents.

Grade: C. The oral and in vitro data do not transfer to the shower.

Green tea (녹차, EGCG)

EGCG is a potent antioxidant, and a 2007 study found it stimulated hair growth in cultured follicles and dermal papilla cells. That is in vitro: cells in a dish, exposed for days. In a rinse-off product, green tea is an antioxidant and a mild astringent, both reasonable things to have on a scalp for a minute.

Grade: C. Good antioxidant. The growth data is from a petri dish.

Hibiscus (히비스커스)

A 2003 study applied hibiscus leaf and flower extract to rats and cultured follicles and reported hair growth effects, with the leaf extract performing better. Rats, and a leave-on extract. Hibiscus is mucilaginous and mildly acidic, which makes it a pleasant conditioning ingredient that helps flatten the cuticle. The traditional Ayurvedic use is for shine and softness, and that is the honest claim.

Grade: C for growth (rodent). B for conditioning, on mechanism.

Camellia oil (동백)

The oil pressed from Camellia japonica seeds, used in Japan and Korea for centuries as a hair oil. It is around 80 percent oleic acid, which makes it a light, penetrating emollient similar to olive oil but less greasy. In a bar it counters the drying effect of surfactants and leaves lengths softer. It does nothing to follicles and does not claim to.

Grade: B as an emollient, on composition. Not a growth ingredient.

Bamboo charcoal (대나무숯)

Activated charcoal has an enormous surface area and adsorbs oils and some impurities on contact. In a cleanser it gives a mild clarifying effect, useful for a scalp with sebum and product buildup. It is also a very fine abrasive, which contributes to gentle physical exfoliation. Claims that it draws toxins from the scalp are not meaningful; the skin is not a reservoir of toxins and charcoal adsorbs surface oil, which is what it is for.

Grade: B for clarifying, on well-understood physical chemistry. Ignore the detox language.

Houttuynia cordata (어성초)

A herb widely used in Korean skincare for reactive, acne-prone skin. Laboratory studies show anti-inflammatory and antimicrobial activity of its extracts. There is no scalp or hair trial. Its role in a cleanser is soothing an itchy, reactive scalp, and it is a sensible inclusion for that purpose on mechanism.

Grade: C. Plausible soothing agent; no human scalp data.

Rosemary (로즈마리)

The botanical with the best human evidence, which is still one 2015 trial of 100 men comparing leave-on oil to minoxidil 2 percent over six months, without a placebo. In a rinse-off product the exposure is a fraction of the trial's, and there is no rinse-off study. Rosemary is an antioxidant and circulatory stimulant in a cleanser, and the trial is a reason for curiosity rather than expectation.

Grade: B for leave-on oil in men. C in a cleanser.

Grapefruit peel (자몽)

Citrus peel extracts are rich in limonene and flavonoids, are mildly astringent, and have antimicrobial activity in the laboratory. In a scalp cleanser grapefruit peel is a clarifying and refreshing agent. It has no hair growth literature. Note that citrus oils can be photosensitising on skin in leave-on use; in a rinse-off product this is not a practical concern.

Grade: C for clarifying. D for anything to do with hair growth.

Saururus chinensis (삼백초)

A herb in traditional Korean and Chinese medicine with laboratory evidence of anti-inflammatory and antimicrobial activity. No scalp or hair study. It is in the same category as houttuynia: a plausible soothing agent with no human scalp data.

Grade: C, on mechanism only.

Chestnut inner bark (율피)

Chestnut shell and inner bark are rich in tannins, which are astringent: they tighten and tone skin surfaces temporarily and reduce surface oil. In a cleanser this reads as a firmer, less oily-feeling scalp after washing. Tannins do not act on the follicle, and there is no hair study.

Grade: C for astringency, which is well understood. Not a growth ingredient.

Peppermint (페퍼민트)

Menthol activates cold receptors in the skin and increases local blood flow briefly, which is the tingle. A 2014 mouse study found peppermint oil at 3 percent promoted hair regrowth in shaved mice faster than minoxidil over four weeks. Mice, with a hair cycle measured in weeks. There is no human data. In a cleanser peppermint is a pleasant, mildly stimulating, antimicrobial ingredient.

Grade: C. The mouse study is real and does not transfer.

What the grades add up to

None of the twelve reaches grade A, and no botanical in any rinse-off scalp product does. The honest role of botanicals in a cleanser is to make the cleansing gentler, the scalp calmer, the lengths softer and the experience one you will repeat daily. Those are real jobs. They are the jobs a good cleanser does, and a good cleanser is what a scalp needs. What it does not need is a promise about follicles borrowed from a mouse, a dish, or a capsule.