Blue mass was recommended as a remedy for such widely varied complaints as tuberculosis, constipation, toothache, parasitic infestations, and the pains of childbirth. It was a magistral preparation, compounded by pharmacists themselves based on their own recipes or on one of several widespread recipes. It was sold in the form of blue or gray pills, or syrup. Its name probably derives from the use of blue dye or blue chalk (used as a buffer) in some formulations.
The ingredients of blue mass varied, as each pharmacist prepared it himself, but they all included mercury in elemental or compound form (often as mercury chloride, also known as calomel). One recipe of the period included (for blue mass syrup):
Mercury is known today to be toxic, and ingestion of mercury leads to mercury poisoning (q.v.), a form of heavy-metal poisoning. While mercury is still used in compound form in some types of medicines and for other purposes, blue mass contained excessive amounts of the metal: a typical daily dose of two or three blue mass pills represented ingestion of more than one hundred times the daily limits set by the Environmental Protection Agency in the U.S. today. Over time, anyone taking blue mass regularly was virtually certain to develop mercury poisoning.
Some historians suspect that Abraham Lincoln's use of blue mass to treat “melancholy” (probably clinical depression) may have altered his behavior, and may explain the erratic behavior and violent rages to which he was subject over a period of years prior to the Civil War in the United States. Lincoln stopped taking it soon after his inauguration as President because it made him “cross,” according to a letter he wrote to a friend. Some historians believe that this explains the contrast between his earlier behavior (while he was perhaps suffering from mercury poisoning from his use of Blue Mass) and his later behavior during the war (after he had stopped taking blue mass), given that most of the effects of mercury poisoning are reversible. Unfortunately, since no hair samples from Lincoln during this period are available, it is impossible to determine whether or not he was truly suffering from mercury poisoning while he was taking the blue mass.
Other famous historical figures, such as Ulysses S. Grant, may also have taken blue mass regularly.