How did Abraham Lincoln’s mother Nancy Hanks Lincoln die?

Nancy Hanks Lincoln, February 5, 1784 – October 5, 1818, died from human milk sickness after drinking the milk from a cow that had grazed on the White Snakeroot. The future president was nine years old when his mother died.

White Snakeroot is a North American herb with a dangerously toxic alcohol called tremetol which contains the chemical compound tremetone. Ingesting any part of the plant can kill you. The poison remains in the milk and meat of the animals that accidentally consume it, and the poison is in turn passed to humans. Nursing calves may have also died from their mothers' milk contaminated with snakeroot, although the adult cows and sheep showed no signs of poisoning. Cattle, horses, and sheep are the animals most often poisoned.The most common symptoms are the loss of appetite, muscle stiffness, constipation, coma, reddened tongue, and weakness.

Human milk sickness is uncommon today in the United States. Current practices of animal husbandry generally control the pastures and feed of cattle, and the pooling of milk from many producers lowers the risk of tremetol.