Comfrey

Several cases of acute liver injury resembling sinusoidal obstruction syndrome (SOS) due to oral comfrey have been published. The injury usually arises within 1 to 2 months of starting the comfrey product (either extract in tablet form or large amounts of comfrey tea) with onset of right upper quadrant pain, nausea and weight gain (from fluid retention) followed by jaundice. Serum aminotransferase levels are usually only mildly elevated with a hepatocellular pattern of injury, although they may be markedly increased if tested during the early phases of the injury. Immunoallergic and autoimmune features are usually not present. The injury can be severe and rapidly lead to acute liver failure (acute sinusoidal obstruction syndrome), but more commonly presents insidiously with weight gain, ascites, weakness, and minimal serum aminotransferase elevations (subacute or chronic sinusoidal obstruction syndrome).