Among the longest living of organisms on the planet, with some clonal groups living over 11,000 years, Larrea tridentata is rich in unpalatable and biologically active chemicals that discourage foraging insects and animals from feeding on it. These same chemicals led to its investigation as an herbal remedy by the early indigenous people of the North American Southwest, and it continues to be used today for many of these original applications. Historically, Larrea tridentata has been used to treat conditions as varied as the common cold, fever, influenza, gout, arthritis, upset stomach and intestinal gas, sinusitis, anemia, tuberculosis, chicken pox, fungal infections and allergy. It has also helped treat autoimmune diseases like rheumatism and lupus as well as premenstrual syndrome (PMS), acute pain, parasitic infection, diarrhea, and cancer. Some of the same bioactive chemicals believed to be responsible for its medicinal properties have also given it a reputation for toxicity, with several controversial cases of liver damage attributed to the use of high doses of Larrea tridentata over long periods of time.
Among the pharmacologically active chemicals present in the resin of Larrea tridentata plants are numerous essential oils, 19 different flavonoids, several halogenic alkaloids, many different lignana, and nordihydroguaiaretic acid (NDGA). While research has suggested that some of the lignans present in the plant resin possess both antimicrobial, anti-inflammatory and antioxidant properties, it is NDGA that has been the focus of most research into the efficacy of the plant. The lignans are known to non-selectively inhibit the pro-inflammatory enzyme cyclooxygenase, producing much of the plants anti-inflammatory effects, while NDGA is believed instead to inhibit electron chain transport in the mitochondria of certain cells. In layman's terms, NDGA is thought to interrupt the growth and energy production of certain types of malignant cells. Several studies have suggested that Larrea tridentata resin may in fact suppress certain types of tumor growth, while also indicating that the same resin may stimulate the growth of other cancers.
While there is ample evidence to suggest that Larrea tridentata has significant promise as a treatment for a number of different illnesses, its use is not without its risks. Some patients may experience side effects like stomach pain, weight loss, rash, fever, nausea, diarrhea or damage to the liver or kidneys. Patients using an extract of Larrea tridentata — any product containing chaparral, greasewood, shegoi, or gubernedora — internally in a form that has not had all suspected toxins removed should be regularly tested for elevation of liver enzymes. The plant may also interact seriously with a number of different medications. Despite the potential risks, many alternative medical practitioners still recommend Larrea tridentata for difficult to treat conditions like shingles, cold sores, genital herpes, eczema, psoriasis, Epstein Barr virus, genital warts, cancer and Bell's palsy.
