Chaparral (Larrea tridentata) and Hepatotoxicity: Why the FDA Warned Against the Desert Detox Herb

Chaparral is the dried leaves and stems of Larrea tridentata, the creosote bush of the American Southwest desert. It has been used in indigenous Sonoran and Mexican folk medicine for centuries and resurfaced in the 1960s wellness counterculture as an internal "detox," anti-cancer, and anti-aging tea. By the 1990s a sufficient number of severe hepatitis cases had been reported that the FDA issued advisories and several distributors recalled products. The clinical and mechanistic picture is unusually clear for an herbal hepatotoxin.

The FDA advisory and case series

In 1992 the FDA issued a warning following at least 13 reports of hepatotoxicity associated with chaparral capsules and teas, including cases of acute hepatic failure and a death [1]. Sheikh and colleagues 1997 reviewed 18 cases of chaparral-associated hepatic injury collected by the FDA and other agencies. The pattern was typically cholestatic or mixed hepatitis appearing 3 to 52 weeks after start of use, with most patients recovering after discontinuation but several progressing to cirrhosis or requiring transplantation [2].

NDGA: the principal toxin

The principal phytochemical in chaparral is nordihydroguaiaretic acid (NDGA), a lignan and potent antioxidant. NDGA was approved by the FDA in the 1950s as a food antioxidant under the name "NDGA" but was withdrawn in 1968 after rodent toxicity studies showed renal and hepatic damage. Subsequent mechanistic work has shown that NDGA undergoes cytochrome P450-mediated oxidation to a reactive ortho-quinone metabolite that forms covalent adducts with hepatocyte proteins and depletes glutathione [3]. The mechanism resembles classical idiosyncratic drug-induced liver injury such as that seen with acetaminophen overdose.

Why hepatic failure can be late

Most patients tolerate chaparral for weeks to months without symptoms because hepatic glutathione reserves are adequate to detoxify the quinone. As supplementation continues or as inter-current illness, malnutrition, or interacting drugs (acetaminophen, certain antiepileptics) deplete glutathione, the metabolite accumulates. Hepatic injury then appears abruptly, often presenting with jaundice, fatigue, and elevated aminotransferases above 1,000 U/L. The acute decompensation in chronic exposure mimics drug-induced autoimmune-like hepatitis on histology, with portal lymphocytic infiltrate and zonal necrosis [4].

Persistent presence in supplements

Despite the FDA advisory, chaparral remains commercially available in the United States as dietary supplements under DSHEA, sold for "internal cleansing," "blood purification," and "antioxidant support." Some products combine chaparral with other hepatotoxic herbs (comfrey, pennyroyal) compounding the risk. NDGA is sometimes sold separately as an "anti-aging" compound based on lifespan extension in C. elegans and Drosophila models — those findings have not translated to clinical use, and the toxicity profile makes them unsuitable for chronic human consumption.

Clinical action

Chaparral has no validated indication and a substantial hepatotoxicity risk. The 2014 LiverTox NIH monograph classifies chaparral as a "likely cause" of clinically apparent acute liver injury [5]. Patients with new-onset hepatitis of unclear etiology should be questioned about chaparral, NDGA, or "creosote bush" exposure, particularly in the southwestern US and among consumers of online wellness or "detox" products. Discontinuation is sufficient treatment in most cases; severe presentations require hospitalization and consideration of N-acetylcysteine.