In the 1800's, John Hoxsey watched a horse recover from cancer after feeding in a field of wild plants and grasses. Hoxsey collected the field plants and formulated an herbal tonic remedy to treat animals suffering various illnesses. For generations the formula for the herbal tonic was kept a Hoxsey family secret, until John Hoxsey's great-grandson Harry Hoxsey, an Illinois coal miner, marketed the herbal tonic as a cancer remedy for humans and promoted himself as a self-taught herbal healer.

During the 1920's, the first Hoxsey clinic opened. During the 1940's and 1950's, the Hoxsey formula was a popular cancer treatment with cancer patients. The Hoxsey clinics were numerous, and at one point, the Dallas clinic was one of the largest privately owned cancer hospitals in the world. After substantial troubles with the American Medical Association, AMA, the National Cancer Institute, NCI, and the Food & Drug Administration, FDA, the clinics and hospital were closed. Mildred Nelson, a nurse in one of the Hoxsey clinics, left the US with the Hoxsey formula, and opened a Hoxsey clinic in Tijuana, Mexico. The Hoxsey formula is used to treat breast cancer, cervical cancer, colon cancer, lung cancer, lymphoma, melanoma, mouth cancer, prostate cancer, sarcomas, normalizing cell metabolism and tumor regression. No human studies have been conducted evaluating the effectiveness or safety of Hoxsey formula.

According to the US National Library of Medicine and the National Institutes of Health, the Hoxsey formula is not a single formula, but a tonic and topical preparation. The formula may be mixed differently, depending on the cancer and condition of the patient. The formula for the tonic includes a mixture of licorice, red clover, burdock root, stillingia root, barberry, Cascara, prickly ash bark, buckthorn bark and potassium iodide. The topical preparation is a red paste containing antimony trisulfide, zinc chloride, and bloodroot and a yellow powder containing arsenic sulfide, sulfure and talc. In addition, Hoxsey clinic patients are required to adhere to strict dietary guidelines, take Vitamin C, and maintain a positive attitude.

According to the University of California Moores Cancer Center, at one time, the University of Texas M.D. Anderson Cancer Center performed an extensive human studies literature review of the Hoxsey treatment and found four studies applicable to cancer.  The studies report response to therapy although none of the studies used controls against which to measure response.  Individual components of the formula have been tested in the laboratory or in animals.  Seven of the nine herbs in the formula have shown some anti-cancer activity.  M.D. Anderson Cancer Center recommended that more studies of both the external and internal components of the Hoxsey formula are needed.

In 1999, Mildred Nelson died, but the Hoxsey clinic in Tijuana, Mexico is still in operation.