Fish Mint

The drug is yu xing cao, literally “fishy-smell herb”: the dried or fresh aerial parts. It is classified as pungent in taste and cool in nature, entering the Lung channel. Its actions are to clear heat and resolve toxicity, drain pus and promote urination.

Its principal indication is lung heat with phlegm and pus: pneumonia, lung abscess, bronchitis and hot cough ^{27Reference 27Wu et al. · 2021ReviewHouttuynia cordata Thunb: an ethnopharmacological review — reviewView study →}. Secondary indications are hot, painful urinary dribbling and, applied as a fresh poultice, sores, carbuncles and inflamed swellings.

The volatile oil is lost with heat, so yu xing cao is added late to a decoction and simmered only briefly, or used fresh.

Across Japan, Korea and Vietnam the leaf is used for digestive complaints, constipation, high blood pressure, high blood sugar, influenza and other viral infections, pneumonia, cough, and kidney and urinary-tract inflammation. It is also applied to insect bites and used as an insect repellent.

In Japan, fresh leaves softened into a poultice are the commonest household use, applied to boils, carbuncles and other pus-filled skin infections ^{11Reference 11Sekita et al. · 2016In vitroAnti-bacterial and anti-inflammatory effects of ethanol extract from Houttuynia cordata poultice — in vitroView study →}.

In north-eastern India the leaves are eaten as a “medicinal salad” to lower blood sugar ^{14Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →}.

The steam-distilled volatile oil reduced xylene-, formaldehyde- and carrageenan-induced swelling in mice. It lowered prostaglandin E2 in the inflamed tissue, and nitric oxide and TNF-α in stimulated mouse macrophages ^{8Reference 8Li et al. · 2013In vitroHouttuynia cordata volatile oil exhibited anti-inflammatory effects in vivo and inhibited nitric oxide and TNF-α in vitro — animal modelView study →}.

The four main leaf flavonoid glycosides, rutin, hyperoside, isoquercitrin and quercitrin, and their aglycone quercetin, each reduced influenza-induced lung injury in mice. Hyperoside and quercitrin were the most effective ^{9Reference 9Tang et al. · 2023AnimalTherapeutic effects on H1N1-induced pneumonia in mice and intestinal biotransformation of four main flavonoids from Houttuynia cordata — animal modelView study →}.

A purified polysaccharide reduced liver injury after ischaemia-reperfusion in mice by suppressing TLR4/NF-κB signalling in macrophages ^{20Reference 20Yu et al. · 2026AnimalHouttuynia cordata polysaccharide alleviates hepatic ischemia-reperfusion injury by regulating macrophage polarization via TLR4/NF-κB — animal modelView study →}.

Gap: No human anti-inflammatory trial, and the three active fractions behave differently — a result for the volatile oil says nothing about a water infusion.

A steam distillate of the fresh plant directly inactivated HSV-1 in vitro without harming the cells. The effect was traced to three volatile components, 2-undecanone (methyl n-nonyl ketone), lauraldehyde and decanal ^{1Reference 1Hayashi et al. · 1995In vitroVirucidal effects of the steam distillate from Houttuynia cordata and its components on HSV-1, influenza virus, and HIV — in vitroView study →}.

Hot-water extracts blocked HSV-2 (IC50 about 50 µg/mL) by inhibiting NF-κB activation, and the major water-soluble flavonoids quercetin, quercitrin and isoquercitrin did the same ^{3Reference 3Chen et al. · 2011In vitroHouttuynia cordata blocks HSV infection through inhibition of NF-κB activation — in vitroView study →}. Water extracts also blocked HSV-1, HSV-2 and acyclovir-resistant HSV-1, mainly by preventing the virus from binding to and entering cells ^{4Reference 4Hung et al. · 2015In vitroHouttuynia cordata targets the beginning stage of herpes simplex virus infection — in vitroView study →}.

The houttuynoids are a type of flavonoid in which a houttuynin chain is attached to a hyperoside core, first isolated from this plant ^{2Reference 2Chen et al. · 2012In vitroHouttuynoids A–E, anti-herpes simplex virus active flavonoids with novel skeletons from Houttuynia cordata — in vitroView study →}. Houttuynoids A–E and M were active against HSV in plaque assays, with IC50 values of about 12 µM for houttuynoid A and 18 µM for houttuynoid M ^{2,6Reference 2Chen et al. · 2012In vitroHouttuynoids A–E, anti-herpes simplex virus active flavonoids with novel skeletons from Houttuynia cordata — in vitroView study →Reference 6Li et al. · 2017In vitroHouttuynoid M, an anti-HSV active houttuynoid from Houttuynia cordata — in vitroView study →}.

Houttuynoid A also inhibited HSV-1 multiplication and prevented skin lesions in an HSV-1-infected mouse model, and was active against HSV-2 and varicella-zoster virus ^{5Reference 5Li et al. · 2017In vitroAnti-herpes simplex virus type 1 activity of Houttuynoid A, a flavonoid from Houttuynia cordata — in vitroView study →}.

Gap: No human herpes study exists, and there is no evidence that a tea, tincture or topical preparation reaches an antiviral concentration in the body.

During the 2003 SARS outbreak houttuynia was shortlisted in China because of its traditional use for pneumonia. A water extract inhibited two SARS-CoV enzymes, the 3C-like protease and the RNA-dependent RNA polymerase, in the laboratory. In mice, it raised CD4+ and CD8+ T cells and IL-2 and IL-10 ^{7Reference 7Lau et al. · 2008In vitroImmunomodulatory and anti-SARS activities of Houttuynia cordata — in vitro / animal modelView study →}.

For influenza, the four main flavonoids reduced H1N1-induced lung injury in mice ^{9Reference 9Tang et al. · 2023AnimalTherapeutic effects on H1N1-induced pneumonia in mice and intestinal biotransformation of four main flavonoids from Houttuynia cordata — animal modelView study →}. A polysaccharide from the plant, which has no direct antiviral or antibacterial action in vitro, improved survival and reduced gut and lung damage in mice co-infected with H1N1 and MRSA, acting through the gut–lung axis ^{10Reference 10Li et al. · 2025AnimalAn anti-complement homogeneous polysaccharide from Houttuynia cordata ameliorates acute pneumonia from viral–bacterial co-infection — animal modelView study →}.

Older in vitro work also reports direct virucidal action against influenza virus and HIV-1 ^{1Reference 1Hayashi et al. · 1995In vitroVirucidal effects of the steam distillate from Houttuynia cordata and its components on HSV-1, influenza virus, and HIV — in vitroView study →}.

Gap: No human antiviral trial of houttuynia alone; the coronavirus case is enzyme-level, and the influenza data are mouse lung-injury models, not infection prevention in people.

A Japanese interview survey found that a poultice of softened fresh leaves was the plant’s most common household use, for boils, carbuncles and other pus-filled skin infections. An ethanol extract of the poultice killed methicillin-resistant Staphylococcus aureus (MRSA), inhibited its biofilms, and reduced IL-8 and CCL20 release from human skin cells ^{11Reference 11Sekita et al. · 2016In vitroAnti-bacterial and anti-inflammatory effects of ethanol extract from Houttuynia cordata poultice — in vitroView study →}.

Essential oils from Indian plants were antibacterial and antifungal, and their composition varied with plant part and season ^{12Reference 12Verma et al. · 2017In vitroChemical composition and allelopathic, antibacterial, antifungal, and antiacetylcholinesterase activity of fish-mint (Houttuynia cordata) from India — in vitroView study →}.

Extracts also inhibited S. aureus and Pseudomonas aeruginosa isolated from diabetic-foot ulcers, including drug-resistant strains, at 31–125 µg/mL ^{13Reference 13Geng et al. · 2025In vitroIn vitro activity of Houttuynia cordata against bacteria isolated from diabetic foot — in vitroView study →}. The same report describes 72 diabetic-foot patients randomised between methicillin, meropenem and houttuynia, with clinical measures improving on houttuynia; the abstract gives few details of that comparison ^{13Reference 13Geng et al. · 2025In vitroIn vitro activity of Houttuynia cordata against bacteria isolated from diabetic foot — in vitroView study →}.

Apart from that brief report, the findings are in vitro, and no controlled human infection trial has been published.

Several streptozotocin-diabetic rat studies point the same way. A standardised extract at 200–400 mg/kg for 21 days lowered fasting glucose and raised insulin. The authors attributed this to increased expression of the glucose transporter GLUT-4 and to antioxidant activity ^{14Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →}.

An ethanolic extract (500 mg/kg for 28 days) and a fermented preparation (100 mg/kg) also lowered blood glucose and improved blood lipids or glucose tolerance in diabetic rats ^{15,16Reference 15Rahman et al. · 2024AnimalImpacts of Plu kaow (Houttuynia cordata) ethanolic extract on diabetes and dyslipidemia in STZ-induced diabetic rats — animal modelView study →Reference 16Sakuludomkan et al. · 2021AnimalEffects of fermented Houttuynia cordata on diabetic rats and on insulin resistance in 3T3-L1 adipocytes — animal modelView study →}.

The work was motivated by the use of the leaf as a “medicinal salad” for blood sugar in north-eastern India ^{14Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →}. All of it is in chemically induced diabetes in rodents, at doses high relative to food intake, and there is no human glucose or HbA1c data.

Oral water extracts inhibited compound 48/80-induced systemic anaphylaxis in mice and local allergic reactions in rats. They stabilised mast cells, reducing degranulation, histamine release and calcium uptake ^{17Reference 17Li et al. · 2005AnimalInhibitory effects of Houttuynia cordata water extracts on anaphylactic reaction and mast cell activation — animal modelView study →}. In mice and rat mast cells, the extract also blocked IgE-mediated responses at several steps of FcεRI signalling, and lowered IL-4 and TNF-α production ^{18Reference 18Han et al. · 2009AnimalHouttuynia cordata water extract suppresses anaphylactic reaction and IgE-mediated allergic response by inhibiting FcεRI signaling in mast cells — animal modelView study →}.

The injectable houttuynia product behaves differently. It is a documented cause of anaphylactoid reactions, which in mice depend on the mast-cell receptor Mrgprb2 (MRGPRX2 in humans) ^{26Reference 26Sun et al. · 2022Mrgprb2 gene plays a role in the anaphylactoid reactions induced by Houttuynia cordata injection — animal / mechanisticView study →}.

Gap: the efficacy data are from mice and rats — and the oral mast-cell-stabilising effect is a separate thing from the injectable houttuynia product’s record of anaphylaxis, which is a real and documented harm.

The leaf is rich in quercetin, quercitrin, hyperoside and rutin, flavonoids with well-characterised radical-scavenging chemistry. In diabetic rats, several extracts restored antioxidant enzymes or lowered oxidative-stress markers ^{14,15,16Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →Reference 15Rahman et al. · 2024AnimalImpacts of Plu kaow (Houttuynia cordata) ethanolic extract on diabetes and dyslipidemia in STZ-induced diabetic rats — animal modelView study →Reference 16Sakuludomkan et al. · 2021AnimalEffects of fermented Houttuynia cordata on diabetic rats and on insulin resistance in 3T3-L1 adipocytes — animal modelView study →}.

No human study has measured antioxidant status.

In HepG2 liver cells, an extract reduced high-glucose-induced fat accumulation, lowered fatty acid synthase and SREBP-1, and activated AMP-activated protein kinase (AMPK) ^{19Reference 19Kang et al. · 2014In vitroHouttuynia cordata attenuates lipid accumulation via AMP-activated protein kinase signaling in HepG2 cells — in vitroView study →}.

In mice, a purified polysaccharide reduced liver injury after ischaemia-reperfusion (lower ALT and AST, less oxidative stress) by shifting macrophages away from an inflammatory state through TLR4/NF-κB ^{20Reference 20Yu et al. · 2026AnimalHouttuynia cordata polysaccharide alleviates hepatic ischemia-reperfusion injury by regulating macrophage polarization via TLR4/NF-κB — animal modelView study →}.

This is one cell study and one animal model, with no human liver data.

Six alkaloids were isolated from the aerial parts: aristolactam B, piperolactam A, aristolactam A, norcepharadione B, cepharadione B and splendidine. Several were cytotoxic to five human cancer cell lines (lung A549, ovarian SK-OV-3, melanoma SK-MEL-2, CNS XF-498 and colon HCT-15) ^{21Reference 21Kim et al. · 2001In vitroCytotoxic alkaloids from Houttuynia cordata — in vitroView study →}.

The essential oil inhibited diffuse large B-cell lymphoma cells and, injected into the abdomen of nude mice, slowed the growth of lymphoma grafts ^{22Reference 22Peng et al. · 2026In vitroHouttuynia cordata Thunb. essential oil inhibits diffuse large B-cell lymphoma growth — in vitro / animal modelView study →}.

These are cell-line and single-model findings. Cytotoxicity to cancer cells establishes neither selectivity nor clinical benefit.

Promoting urination is one of houttuynia’s actions in Chinese medicine, and “diuretic” appears among its listed properties in modern papers ^{13Reference 13Geng et al. · 2025In vitroIn vitro activity of Houttuynia cordata against bacteria isolated from diabetic foot — in vitroView study →}.

No modern study has measured urine output or electrolyte excretion.

Food use. Houttuynia is eaten as a leaf vegetable across East and South-East Asia and is generally well tolerated. In an acute test, an oral water extract was non-toxic to laboratory animals at 16 g/kg ^{7Reference 7Lau et al. · 2008In vitroImmunomodulatory and anti-SARS activities of Houttuynia cordata — in vitro / animal modelView study →}.

Allergy. It can cause allergic reactions in sensitive people.

Aristolactams. The plant contains aristolactams, relatives of the kidney-damaging and carcinogenic aristolochic acid I. In a 2025 mouse study, the main aristolactams (AL I and AL BII) caused only modest kidney changes compared with aristolochic acid I. Less of them was absorbed (about 53% and 40%, against 100% for aristolochic acid I), and they were metabolised to less toxic forms. The authors concluded that typical dietary consumption is likely safe, and that aristolactam content should be monitored ^{24Reference 24Xue et al. · 2025AnimalSafety evaluation of aristolactams from the edible herb Houttuynia cordata: implications for dietary exposure and food safety — animal modelView study →}.

The injectable product. Houttuynia injection, used in Chinese hospitals, is a separate medicine from the oral herb. A systematic review of 1,232 adverse-reaction reports found that anaphylactic shock made up about 59% of the most serious reactions, and all but one of the reported deaths were from allergic shock. Intravenous injection carried more risk than intramuscular, and combining the injection with macrolide antibiotics raised the risk about ninefold ^{25Reference 25Wang et al. · 2010Systematic reviewAdverse events to Houttuynia injection — systematic reviewView study →}. None of this applies to eating the plant or taking it by mouth.

Interactions. The only documented interactions concern the injectable product given with antibiotics ^{25Reference 25Wang et al. · 2010Systematic reviewAdverse events to Houttuynia injection — systematic reviewView study →}. No drug or CYP450 interaction has been studied for the oral herb.