White snakeroot, scientifically known as Ageratina altissima, is a perennial herb commonly found across eastern and central North America. Despite its appearance as an unassuming wildflower, especially when its white blossoms emerge in late summer and fall, this plant is highly toxic. It has a notable history due to its association with “milk sickness,” a serious illness that historically posed a significant health risk to humans and livestock.
The Toxic Compound
White snakeroot contains toxic compounds that can harm humans. The primary culprit is tremetol, a fat-soluble alcohol. This complex mixture includes several chemically related substances, with tremetone being a significant constituent. Tremetol is present throughout the entire plant, affecting all parts whether the plant is fresh or dried.
Pathways of Exposure
Humans can be exposed to white snakeroot’s toxins through two main pathways: direct and indirect ingestion. Direct exposure occurs if someone accidentally consumes parts of the plant. Indirect ingestion, known as “milk sickness,” historically presented a more widespread risk.
Milk sickness develops when livestock, particularly cattle, graze on white snakeroot. The tremetol from the plant then accumulates in their milk and meat. Humans who consume these contaminated dairy or meat products can become poisoned. This indirect transmission was a significant public health concern in the 19th century, leading to many illnesses and deaths among settlers. Though less common now due to modern agricultural practices, the risk of milk sickness persists if animals consume the plant and their products enter the food chain.
Symptoms of Poisoning in Humans
Ingestion of tremetol, whether directly or indirectly, can lead to a range of severe symptoms in humans. Initial signs often include digestive disturbances such as nausea, vomiting, abdominal pain, and loss of appetite. Individuals may also experience constipation and a distinct foul-smelling breath, sometimes described as having an acetone odor. As the poisoning progresses, other symptoms can manifest, including weakness, severe thirst, and muscle tremors.
In more severe cases, the toxins can cause significant damage to internal organs. Liver damage and kidney failure are possible outcomes, and the illness can lead to delirium, coma, and even death. The severity of symptoms depends on the amount of toxin ingested, and the effects may take several days to appear, making early detection challenging. Weakness can persist for weeks even in individuals who survive.
Identification and Prevention
Identifying white snakeroot is important for preventing exposure. This perennial plant typically grows between 2 to 5 feet tall, with smooth, upright stems. Its leaves are opposite, broadly ovate or heart-shaped, with serrated or toothed edges, and noticeable veins. The plant is most recognizable in late summer and fall, from July through October, when it produces clusters of small, fluffy white flowers at the ends of its branches.
White snakeroot thrives in shaded or partially shaded environments, commonly found in woodlands, thickets, forest edges, and disturbed areas like roadsides and old fields. It prefers moist soils but can tolerate drier conditions.
Prevention involves several practical steps:
Remove white snakeroot from pastures, gardens, and other areas accessible to humans and livestock.
Wear gloves and dispose of the plant carefully when clearing it to avoid contact.
Exercise caution when foraging for wild plants, as white snakeroot can be mistaken for other, non-toxic species.
Ensure livestock are not allowed to graze in wooded or overgrown areas where white snakeroot is prevalent.
Provide supplemental feed in pastures to reduce the likelihood of animals consuming the plant, especially during dry periods when other forage is scarce.
If exposure is suspected, seeking immediate medical attention is advisable.