Crude drugs derived from Equisetum arvense include Wenjing, Jiejiecao, and Bitoucai.
Note: Equisetum arvense should not be confused with members of the genus Laminaria, kelp, or brown alga, for which "horsetail" has been used as a synonym.
Horsetail (Equisetum arvense) has traditionally been used in Europe as a diuretic for the treatment of edema (swelling/fluid retention). The German Commission E expert panel has approved horsetail for this indication. Horsetail is also occasionally used for osteoporosis, nephrolithiasis (kidney stones), urinary tract inflammation, and wound healing (topical). It is also used in cosmetics and shampoos. These uses have largely been based on anecdote and clinical tradition, rather than scientific evidence.
There is preliminary human evidence supporting the use of horsetail as a diuretic. One poorly designed human trial found horsetail to effectively raise bone density equally to calcium supplements.
In theory (based on mechanism of action), horsetail ingestion in large amounts may cause thiamine deficiency, hypokalemia (low potassium), or nicotine toxicity. Reported adverse effects include dermatitis.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Diuresis (increased urine):
Use of horsetail dates to ancient Roman and Greek medicine. The name Equisetum is derived from equus, "horse," and seta, "bristle." Preliminary human and laboratory research suggests that horsetail may increase the amount of urine produced by the body. More studies are needed to determine if horsetail is safe or useful for specific health conditions.
Osteoporosis (weakening of the bones):
Silicon may be beneficial for bone strengthening. Because horsetail contains silicon, it has been suggested as a possible natural treatment for osteoporosis. Preliminary human study reports benefits, but more detailed research is needed before a firm recommendation can be made. People with osteoporosis should speak with a qualified healthcare provider about possible treatment with more proven therapies.