Milk sickness, usually called milksick by early nineteenth-century American pioneers, denotes what we now know to be poisoning by milk from cows that have eaten either the white snakeroot or the rayless goldenrod plants. The white snakeroot, common in the Midwest and upper South, is a member of the Compositae called Eupatorium urticaefolium. It is also known as white sanicle, squaw weed, snake weed, pool wort, and deer wort. A shade-loving plant, it is frequently seen growing on roadsides, in damp open areas of the woods, or on the shaded north side of ridges. The rayless goldenrod, Haplopappus heterophyllus, is the cause of the disease in southwestern states, such as Arizona and New Mexico.

Milk sickness has been called variously alkali poisoning, puking disease, sick stomach, the slows or sloes, stiff joints, swamp sickness, tires, and trembles (when it occurs in animals). It is now known as tremetol poisoning after an identified toxic ingredient of the white snakeroot and rayless goldenrod. Tremetol, obtained from the leaves and stems of these plants by extraction with ether, is an unsaturated alcohol with the empirical formula C16H22O3. In consistency and odor, it resembles turpentine.

Distribution and Incidence

Milk sickness was unknown in Europe or in any other region of the world except North America. It appeared in North Carolina as early as the American Revolution near a mountain ridge named Milk Sick. Its highest incidence was in dry years when cows wandered from their brown pastures into the woods in search of forage. As more forests were cleared so that cattle had more adequate pasture, and as fences were built, the incidence of milk sickness decreased rapidly.