C
FAD); Indolent Ulcer (2; JAD); Inflammation (2; APA; CAN; KOM; PH2; WAM); Itch (f; APA);
Leukorrhea (f; CRC; MAD); Mastosis (1; FAD; FEL); Metrorrhagia (f; FEL); Myosis (1; WAM);
Nephrosis (f; CRC; MAD); Ophthalmia (f; CRC); Osteosis (f; PH2); Pain (1; CAN); Pertussis
(f; CRC); Pharyngosis (1; PHR; PH2); Phthisis (f; MAD); Pleurosis (f; PHR; PH2); Psoriasis
(1; APA; PNC); Pulmonosis (f; CRC); Rash (1; APA); Respirosis (f; MAD); Rheumatism (1;
CRC; PH2; PNC); Scrofula (f; CRC; FEL); Sore Throat (f; CRC; PH2); Sprain (2; CRC; KOM;
PH2; SHT); Stomatosis (f; CRC); Strain (1; APA; SHT); Sunburn (f; APA); Swelling (f; MAD);
Tendovaginosis (1; PH2); Tonsilosis (f; CRC); Tuberculosis (f; MAD); Tumor (1; FAD); Ulcer
(f; CRC; MAD); Ulcus cruris (1; FNF; MAD);Vaginosis (f; CRC; PH2); Varicosis (f; PED); VD
(f; DEM); Wound (1; APA; CAN; MAD); Yeast (f; CRC).
Dosages (Comfrey) — Do not use (APA); do not use root (JAD); 2–4 g root as tea 3 ×/day
(CAN); 2 tsp (= ~7.4 g) root in hot tea (MAD); 2–4 ml liquid root extract (PNC); 2–4 ml liquid
extract (1:1 in 25% ethanol) 3 ×/day (CAN); 2–8 ml liquid leaf extract (1:1 in 25% alcohol) 3
×/day (CAN); 2–8 g leaf in tea 3 ×/day (CAN); 0.25–0.5 cup fresh leaf (PED); 6–12 g dry leaf
(PED); 9 g dry leaf:45 ml alcohol/45 ml water (PED); 1–3 cups tea/day (5–10 g herb) remem-
bering PAs (PH2).
Contraindications, Interactions, and Side Effects (Comfrey) — Class 2a, 2b, 2c, 2d. Long-
term use discouraged (AHP). Commission E reports the herb, leaf, and root permitted for
external use only. Skin should be intact and pregnant users should first consult physician.
External dosage of pyrrolizidine alkaloids (PAs) maximum 100 g/day for a maximum 4–6
weeks/year (AEH). Comfrey root may cause liver damage if taken internally (WAM). Contains
PAs. Internal use may cause severe hepatic damage. PAs are toxic to humans, with liver damage
with cirrhosis and ascites, or seneciosis, or veno-occlusive disease (VOD) reported in almost
all cases of severe or fatal intoxications, from intakes of 0.5 mg/kg to 3.3 mg/kg (AEH1).
Chronic comfrey use implicated in at least one instance of hepatic VOD (PNC). Effective July
1996, the AHP Board of Trustees recommends that all products with botanical ingredient(s)
that contain toxic PAs, including Borago officinalis, display the following cautionary statement
on the label, “For external use only. Do not apply to broken or abraded skin. Do not use when
nursing” (AHP). CAN cautions the PAs are genotoxic, carcinogenic, and hepatotoxic. Because
of the PAs, its use in pregnancy and lactation is to be avoided. Animal studies document
placental transfer and secretion into breast milk of unsaturated PAs (CAN). May speed up
metabolism of other drugs (stimulates metabolism of aminopyrine-N-demethylase, a drug
metabolizing enzyme) (CAN). Internal use for more than 4–6 weeks is discouraged (SHT).
Canadians do not allow in food (Blackburn, 1993). “No human being or animal should eat,
drink, or take comfrey in any form” (Br. Med. J. 6163: 596; 1979). According to studies
reported in the Lawrence Review of Natural Products, rats fed comfrey roots or leaves for 600
days developed hepatocellular adenomas, with signs of liver toxicity developing within 180
days. Urinary bladder tumors developed also, even in those on the lowest levels of comfrey.
The incidence of liver tumors was higher with dietary roots than with dietary comfrey leaves.
Alkaloids of Russian comfrey caused chronic liver damage and pancreatic islet cell tumors
after 2 years administration in animal models (LRNP, October 1990).
Extracts (Comfrey) — Extracts antiinflammatory in vitro and in vivo, perhaps due to rosmarinic
acid (PNC). Allantoin a well known dermatological agent (PNC). Aqueous extract stimulates release
of prostaglandin-like material from rat gastric mucosa (PNC). Two nonhepatotoxic PAs, platyphyl-
line and sarracine, have been used for GI hypermotility and peptic ulceration. Yes, aqueous extracts
increase survival time of mice with spontaneous tumors, and decrease tumor growth, and have
antimutagenic activity (PNC). Is comfrey more likely to cause, cure, or prevent cancer? This is
what we really should be studying.