Oxalic acid is an organic compound characterized by its ability to act as a reducing agent. Regarding acid strength, it is considered a weak acid, though a relatively strong one compared to other weak acids. In addition, oxalate, the conjugate base of oxalic acid (the compound produced when oxalic acid loses a hydrogen atom), acts as a chelating agent, or metal binder.

oxalic acid

This compound is found naturally in sheep sorrel and Turkish rhubarb, two of the herbs in Essiac. Other plants in which oxalic acid occurs naturally include some types of spinach, cranberries, chard, and jack-in-the-pulpit, in addition to being a byproduct of bacterial carbohydrate metabolism.

Commercial applications of oxalic acid include but are not limited to incorporation into bleaches, other cleaning supplies, rust-removing agents, baking powder, and aiding with beekeeping. When ingested in large quantities, oxalic acid can be highly toxic. The amount of oxalic acid in Essiac falls well below toxic levels, though.

Oxalic Acid’s Effects on Health

The ability of oxalic acid to chelate, or bind, calcium is the main factor that contributes to the compound’s role in health. Calcium oxalate crystals constitute the most common component of kidney stones, and ingestion of Essiac can predispose people to more frequent stones. Because of this, Essiac is not advised for those with history of kidney stones. Those with any type of kidney disease should also avoid Essiac, as calcium oxalate will not be cleared effectively, thus also potentially leading to kidney stones and possible further organ damage due to blockage of urine flow by a stone.

This chelating property also makes different types of arthritis a relative contraindication to Essiac use. Osteoarthritis or degenerative arthritis, the most common type of arthritis, can be aggravated by Essiac due to decreased calcium absorption. If one insists on using Essiac with concurrent osteoarthritis, though, calcium supplementation is recommended by many naturopathic practitioners.

Another category of arthritis is the inflammatory type, which includes the autoimmune disease rheumatoid arthritis and crystal-induced gout. Acidic foods are pro-inflammatory, and thus, ingestion of oxalic acid can worsen these conditions, also. This concept applies to other inflammatory disorders, as well.


This discussion may raise the question of whether or not calcium chelation by Essiac causes clinically significant calcium deficiency. Most health and dietary authorities agree that the decrease in available calcium is inconsequential, and thus supplementation is not required for most people.

While Essiac is commonly used for a variety of health conditions, there are some mostly benign side effects and relative contraindications. Some of these side effects and contraindications, namely kidney stones and/or damage, arthritis, and inflammatory disease, are related to the oxalic acid content in Essiac. It is important to be mindful of these and other conditions that may be aggravated when taking Essiac or any other herbal supplement.