Houttuynia cordata: the calming ingredient explained
By Dr. Soo-Jin Kim · Seoul Cosmetic Chemist & Senior Editor, K-Ingredient
Updated Jun 2026Houttuynia cordata is a heart-shaped leaf that grows wild across Korea, Japan, and China, and over the past few years it has become one of the most hyped "calming" ingredients in Korean skincare. Brands put it in toners, pads, ampoules, and masks, and call it heartleaf, eojahsi, or fish-mint. This guide walks through what the plant actually contains, what the research really shows, where that evidence is thin, and how heartleaf stacks up against the other calming stars of K-beauty.
Houttuynia cordata is a heart-shaped leaf that grows wild across Korea, Japan, and China, and over the past few years it has become one of the most hyped "calming" ingredients in Korean skincare. Brands put it in toners, pads, ampoules, and masks, and call it heartleaf, eojahsi, or fish-mint. This guide walks through what the plant actually contains, what the research really shows, where that evidence is thin, and how heartleaf stacks up against the other calming stars of K-beauty.
What Houttuynia cordata is
Houttuynia cordata Thunb. is a low-growing perennial herb in the Saururaceae family. The name "cordata" means heart-shaped, which is where the marketing term "heartleaf" comes from. It has been used in traditional East Asian medicine for centuries, mostly as a detox herb, a poultice for skin infections, and a treatment for coughs and inflammation.
In Korea, the plant carries cultural weight. It grows almost like a weed in many regions, and people have long brewed it as a tea or pounded the leaves into a paste for irritated skin. K-beauty brands leaned into that heritage story, and "heartleaf" became a shorthand for gentle, soothing, plant-based care. You will see it on ingredient labels under the International Nomenclature of Cosmetic Ingredients (INCI) name Houttuynia Cordata Extract.
It is worth separating the folklore from the chemistry. The traditional reputation is real and old, but reputation is not the same as proof. Most of the modern science sits in test tubes and animal models, with only a sliver of human cosmetic data. That gap matters, and this guide will keep coming back to it.
What is actually in the leaf
Heartleaf owes its activity to two main groups of compounds: flavonoids and a smelly essential oil.
The flavonoids are the part skincare cares about most. The big four are quercetin, quercitrin, hyperoside, and afzelin, plus rutin and apigenin. These are antioxidant polyphenols, and several of them have measurable anti-inflammatory effects in lab studies. A 2018 review in the Journal of Ethnopharmacology singled out afzelin, hyperoside, and quercitrin as the flavonoids doing most of the anti-inflammatory and antioxidant work (review of inflammation and oxidative stress).
The essential oil is the source of the plant's famous fishy smell. It contains compounds like 2-undecanone, decanoyl acetaldehyde (the so-called "houttuynin"), and sodium houttuyfonate. This fraction drives much of the antibacterial and antiviral activity studied in the lab, but it is also the part most likely to smell off in a finished product. Most well-formulated cosmetics use a refined water-soluble or flavonoid-rich extract, so the toner on your shelf usually does not reek of fish.
How heartleaf is supposed to work
When brands say heartleaf "calms" skin, they are pointing at a few specific lab-documented mechanisms. None of these were measured on your face. They were measured on cells in a dish or on lab mice. Keep that in mind as you read.
Dialing down inflammation signals
Inflammation in skin runs through a handful of master switches. Two of the most important are NF-κB and the MAPK pathways (p38 and JNK). When these get flipped on, skin cells pump out inflammatory messengers like IL-6, IL-8, TNF-α, and IL-1β, plus enzymes like COX-2 and iNOS that drive redness and swelling.
In lab studies, Houttuynia cordata extract and its flavonoids quiet these switches. An ethyl acetate fraction of the extract suppressed NF-κB activity and blunted p38 and JNK activation in stimulated immune cells. The downstream result was lower output of those inflammatory messengers. This is the core "calming" story, and it is reasonably consistent across multiple cell-based papers (PubMed: Houttuynia cordata skin anti-inflammatory).
Mopping up free radicals after UV
A 2022 in-vitro study looked at heartleaf and UVB-damaged human skin cells. Researchers used HaCaT keratinocytes (a standard lab skin-cell line) and zapped them with UVB. Pretreating the cells with the ethyl acetate extract, or with purified quercitrin or hyperoside, protected them from dying.
The mechanism was twofold. The extract reduced the pro-death signals (p38, JNK) while boosting pro-survival ones (ERK1/2, Akt), and it cranked up Nrf2, a transcription factor that turns on the cell's own antioxidant enzymes like SOD1 and HO-1. It also lowered UVB-induced IL-6, IL-8, COX-2, and iNOS. The extract used in that paper was rich in quercitrin (about 287 mg/g) and hyperoside (about 231 mg/g) (UVB keratinocyte study).
This is genuinely interesting science. It is also a dish of cells, not human skin, and it does not mean heartleaf replaces sunscreen. It does not.
Antibacterial and oil-control angle
Heartleaf has measurable antibacterial activity in the lab, including against bacteria linked to acne. Combined with its anti-inflammatory profile, that is why it gets marketed for oily and breakout-prone skin rather than purely for dryness. There is also human cosmetic data suggesting it lowers surface sebum, which we will cover in the evidence section below.
Calming allergic and itch responses
Several animal and cell studies show heartleaf flavonoids can stabilize mast cells and reduce histamine release and IgE-driven responses. That is the basis for the "anti-allergic" and anti-itch claims you see attached to the ingredient. Again, the data is preclinical, and "reduces histamine in a mouse" is a long way from "stops your eczema flare."
The actual evidence, graded honestly
Here is the part that matters most for a YMYL ingredient. Most heartleaf claims rest on test-tube and animal work. Human clinical data is small and mostly about cosmetic endpoints, not disease treatment. The table below grades the main claims by the strength of evidence behind them.
| Claim | Best evidence type | Strength | Honest read |
|---|---|---|---|
| Reduces inflammation signals (NF-κB, MAPK, cytokines) | In-vitro cell studies, animal models | Moderate (preclinical) | Mechanism is well documented in cells, but not proven on human skin in controlled trials |
| Antioxidant / protects cells from UVB damage | In-vitro HaCaT keratinocyte study | Weak-moderate (preclinical) | Real lab finding; does not translate to "sun protection" and is not a sunscreen substitute |
| Lowers facial sebum (oil) | One human cosmetic trial of a heartleaf toner | Weak (single small study, cosmetic) | Promising direction, but one industry-style cosmetic study is not strong proof |
| Improves skin hydration | Same single human cosmetic trial | Weak | Statistically significant in that study only; needs replication |
| Helps acne | In-vitro antibacterial + anti-inflammatory data | Weak (preclinical, indirect) | Plausible support ingredient, not a proven acne treatment |
| Eases atopic dermatitis / eczema | Animal models, lab skin-permeation studies | Weak (preclinical) | Mouse and cell data only; no robust human eczema trials |
| Anti-allergic / anti-itch | Animal and cell studies | Weak (preclinical) | Mechanistically plausible, clinically unproven in skin |
The one human cosmetic study worth knowing
There is a 2023 study (published in the journal Cosmetics) that developed a facial toner with Houttuynia cordata extract and ran an 8-week human use test. The headline numbers: surface sebum dropped significantly more with the heartleaf toner than with the extract-free version, and the paper reported an anti-seborrheic (oil-reducing) efficacy around 31% after 8 weeks. Skin moisture also rose significantly from week 8, running roughly 1.4 to 1.5 times higher than the control toner on the cheeks (PubMed: Houttuynia cordata cosmetic).
That sounds great, and the direction is encouraging. But read it with a cold eye. It is a single study. It tested one specific formula, not heartleaf in general. The sample was small, the endpoints were cosmetic (sebum and moisture meters, not a disease), and studies designed to support a product's marketing tend to find favorable results. This is the strongest human skincare evidence heartleaf has, and it is still weak by clinical-trial standards.
The atopic dermatitis story is preclinical
You will see heartleaf pitched for eczema. The supporting work is almost entirely in mice and cell models. One study built lipid nanocarriers (liposomes and cubosomes) to push a water-soluble heartleaf extract deeper into skin and tested it on dermatitis-like lesions in hairless mice (anti-atopic efficacy study, PMID 23886304). More recent work showed heartleaf polysaccharides reduced skin lesions, mast cell infiltration, and inflammatory cytokines while restoring barrier proteins, again in mice. None of this is a human eczema trial. If you have diagnosed atopic dermatitis, heartleaf is a maybe-soothing extra, not a treatment.
Where the quercitrin anti-inflammatory claim comes from
The flavonoid quercitrin has its own track record. A 1993 pharmacological study of Houttuyniae herba documented the anti-inflammatory effect of quercitrin in animal models (quercitrin anti-inflammatory, PMID 8492297). That is a real, decades-old finding and part of why the ingredient earned its calming reputation. It is still animal and lab data, though. The honest summary across all of this: heartleaf has a believable anti-inflammatory mechanism and a thin layer of human cosmetic data on top (PubMed: Houttuynia cordata quercitrin).
Heartleaf versus the other calming ingredients
Heartleaf does not exist in a vacuum. K-beauty has a whole calming aisle, and the question most people actually have is which one to pick. Here is a sober head-to-head.
| Ingredient | Best for | Evidence level | Texture / vibe | Watch-outs |
|---|---|---|---|---|
| Houttuynia cordata (heartleaf) | Oily, acne-prone, redness with oiliness | Mostly preclinical + 1 human cosmetic study | Light, watery, often in toners and pads | Possible fishy smell in cheap extracts; thin human data |
| Centella asiatica (cica) | Sensitive, compromised barrier, healing | Better human data than heartleaf, including wound and barrier studies | Soothing, works in creams and serums | Can be over-hyped; quality of extract varies |
| Mugwort / Artemisia | Reactive, itchy, irritated skin | Preclinical, traditional use | Often dark herbal essences and oils | Botanical, small allergy risk |
| Panthenol (provitamin B5) | Any irritated or dry skin | Strong, well-established humectant and soothing data | Slippery, universal | Very few; extremely well tolerated |
| Madecassoside (cica fraction) | Redness, barrier repair | Good for an isolated botanical compound | Refined, in serums and creams | Pricier |
The practical takeaway: if your main issue is oily, congested, occasionally red skin, heartleaf is a sensible pick. If your skin is dry, thin, or genuinely sensitive and reactive, centella (cica) and panthenol have stronger and more relevant human evidence. They are not rivals so much as different tools, and layering a heartleaf toner under a cica or panthenol cream is a perfectly reasonable routine. For a deeper look at how heartleaf and mugwort sit together in the botanical calming family, see our guide on mugwort, artemisia and heartleaf in Korean skincare, and for the cica side of the comparison, the centella asiatica science breakdown.
How heartleaf shows up in products
Heartleaf is most common in toners, essences, and exfoliating pads, because it is water-soluble and plays nicely in lightweight watery formats. The famous "99% heartleaf" or "100% heartleaf extract" toners use the leaf-water extract as the main base instead of plain water.
Concentration and what it means
A high percentage number on the label looks impressive, but it can mislead. "77% heartleaf extract" usually means the extract (which is itself mostly water) makes up most of the formula, not that the bottle is packed with active flavonoids. The amount of actual quercitrin, hyperoside, and other actives can be modest even in a high-percentage product. Concentration claims are marketing-friendly and chemistry-vague, so do not over-read them.
Common product types
- Heartleaf toners: the entry point, used to hydrate and calm after cleansing.
- Heartleaf pads: soaked exfoliating or soothing pads, often pairing heartleaf with a mild acid for oily skin.
- Ampoules and serums: more concentrated, sometimes blended with niacinamide, panthenol, or centella.
- Sheet masks and creams: heartleaf as a supporting calming player.
You can see how heartleaf pads landed in the market in our review of the Abib heartleaf spot pad, and how calming ingredients get built into routines in our guide to Korean sheet masks for calming irritated skin.
Safety: what we know and do not know
Topical heartleaf is generally well tolerated, and that is reflected in both its long traditional use and the cosmetic literature. But "generally safe" is not the same as "risk-free," and there are a few real caveats.
Topical use looks low-risk
Animal toxicity studies found no observed adverse effects at high oral doses (no harm seen up to nearly 1000 mg/kg in rats), which supports a wide safety margin for the small amounts used in cosmetics (review of inflammation and oxidative stress). In the human toner study, the formula was reported as safe for daily use over 8 weeks. As a leaf extract, heartleaf is a botanical, so the usual botanical caveat applies: any plant extract can occasionally trigger irritation or an allergic reaction in a sensitive person. Patch test a new product on your inner arm for a couple of days before putting it on your face.
The injection warning does not apply to your toner, but it is worth understanding
You may run into scary headlines about Houttuynia cordata causing anaphylactic shock. Those reports come from injectable heartleaf preparations used in some hospital settings in China, not from skincare. Injected herbal extracts have caused serious allergic reactions, especially when combined with certain antibiotics (ethnopharmacological review). A topical toner is a completely different exposure route and risk profile. Do not let the injection news scare you off a toner, but do know the distinction so you can read claims accurately (PubMed: Houttuynia cordata safety review).
Pregnancy, kids, and broken skin
There is no strong human safety data for heartleaf during pregnancy or breastfeeding, and traditional medicine sometimes used it internally in ways that are not relevant to a face toner. As a topical cosmetic, it is likely fine, but if you are pregnant, nursing, or treating a child, run new actives past your doctor. On broken or oozing skin, or an active eczema flare, see a clinician rather than self-treating with a botanical toner.
Who heartleaf is actually for
Heartleaf fits some skin types better than others. Here is the practical sort.
Good fit:
- Oily and combination skin that gets shiny by midday
- Mild acne and congestion, especially with redness around breakouts
- People who want a lightweight, watery calming step that will not feel greasy
- Anyone building an oil-balancing routine who wants a botanical hydrating toner
Less ideal:
- Very dry or dehydrated skin that needs richer occlusives (heartleaf hydrates lightly but will not seal moisture in)
- Genuinely sensitive, reactive, or barrier-damaged skin, where centella and panthenol have stronger relevant evidence
- Anyone expecting it to clear acne or eczema on its own; it is a supporting calmer, not a treatment
If you are mapping out a full routine around calming and oil control, our Korean skincare routine for acne-prone skin shows where a heartleaf step naturally fits.
How to use it well
Keep it simple. Heartleaf is a low-drama support ingredient, and you do not need to overthink it.
- Cleanse, then apply a heartleaf toner or essence to damp skin with hands or a cotton pad.
- Layer your usual serum (niacinamide, peptides, whatever you already use) on top.
- Seal with a moisturizer. Heartleaf hydrates lightly, so dry skin still needs a proper cream.
- Sunscreen every morning. The antioxidant lab data is not sun protection.
- Patch test any new heartleaf product first, especially if your skin reacts to botanicals.
You can use heartleaf morning and night. It layers fine with most actives, including acids and retinoids, though if your skin is already irritated from a strong active, lean on the gentlest formula and fewer steps.
The bottom line
Houttuynia cordata is a real plant with a real, lab-documented anti-inflammatory mechanism and a single supportive human cosmetic study on oil and hydration. That makes it a reasonable, gentle calming ingredient, especially for oily and breakout-prone skin. It is not a miracle, not a proven acne or eczema treatment, and not backed by the kind of large human trials that would let anyone make strong medical claims. Treat it as a pleasant, low-risk support step, pair it with better-proven actives where it counts, and keep your expectations grounded.
Frequently Asked Questions
Is Houttuynia cordata the same as heartleaf?
Yes. "Heartleaf" is the common English marketing name for Houttuynia cordata, named for the plant's heart-shaped leaves. On ingredient labels it appears as Houttuynia Cordata Extract. You may also see it called eojahsi (its Korean name) or fish-mint, a nod to the essential oil's distinctive smell.
Does heartleaf actually help with acne?
It may help as a supporting ingredient, but it is not a proven acne treatment. Heartleaf has antibacterial and anti-inflammatory activity in lab studies, and one human cosmetic study found a heartleaf toner reduced surface oil. That is plausible support for oily, breakout-prone skin, but the human evidence is thin. For actual acne, proven actives like benzoyl peroxide, adapalene, or salicylic acid do the heavy lifting.
Can heartleaf replace my sunscreen?
No. The "UV protection" claim comes from a lab study on skin cells in a dish, where the extract reduced UVB-driven damage and inflammation markers. That is antioxidant support, not a measured SPF on human skin. Heartleaf does not block UV rays. You still need a broad-spectrum sunscreen every morning, and heartleaf can sit underneath it as a calming step.
Why does some heartleaf skincare smell fishy?
The plant's essential oil contains compounds that produce a fishy or earthy odor, which is why one of its nicknames is fish-mint. Most modern cosmetics use a refined, flavonoid-rich or water-soluble extract that minimizes the smell, so a well-formulated toner usually does not reek. A strong fishy scent often points to a cruder, less processed extract.
Is heartleaf safe for sensitive skin?
Topically it is generally well tolerated and low-risk, but it is still a botanical extract, and any plant compound can occasionally irritate or trigger an allergy in sensitive people. If your skin is genuinely reactive or your barrier is damaged, centella (cica) and panthenol have stronger, more relevant human safety and soothing data. Patch test any new heartleaf product on your inner arm for a couple of days before applying it to your face.
This article is for general information only and is not medical advice. For persistent acne, eczema, or any skin condition, consult a dermatologist or qualified clinician.