Poison hemlock is a highly toxic plant found across many regions of the United States. Unlike poison ivy or wild parsnip, poison hemlock does not typically cause a rash upon contact. Its primary threat comes from potent internal toxins.
Poison Hemlock’s True Impact
Poison hemlock does not cause a contact rash or dermatitis. While minor irritation might occur for some, this is not its primary toxic effect. The plant’s danger stems from highly toxic piperidine alkaloids, such as coniine, N-methyl coniine, and gamma-coniceine, present in all parts of the plant, including leaves, stems, roots, and seeds.
These neurotoxic alkaloids can be absorbed through broken skin, mucous membranes, or, most commonly, through ingestion. Once in the body, they disrupt the nervous system, affecting neuromuscular junctions that control muscle movement. Symptoms can appear rapidly, often within 15 minutes to an hour after ingestion.
Initial symptoms often include nausea, vomiting, excessive salivation, dizziness, and muscle weakness or trembling. As toxins progress, more severe effects can develop, such as dilated pupils, rapid but weak pulse, confusion, and lack of coordination. The most dangerous outcome is respiratory paralysis, leading to death. There is no antidote for poison hemlock poisoning; treatment focuses on managing symptoms and providing supportive care.
Spotting Poison Hemlock
Identifying poison hemlock is crucial due to its high toxicity and resemblance to other plants. It is a biennial plant that can grow quite tall, typically ranging from 3 to 10 feet in height. A distinguishing feature is its smooth, hollow stems, often covered with distinctive purple spots or blotches, particularly near the base.
The leaves are dark green, finely divided, and fern-like, appearing lacy. They are typically triangular and arranged alternately on the stem. When crushed, the foliage often emits an unpleasant, mousy odor, which can help differentiate it from other plants.
During its second year, poison hemlock produces clusters of small, white flowers arranged in umbrella-like formations called umbels, similar to those found in the carrot family. These flower clusters can be 3 to 6 inches across. Poison hemlock is often confused with wild carrot (Queen Anne’s Lace), wild parsnip, and cow parsley.
What to Do After Exposure
Immediate action is important if you suspect contact with or ingestion of poison hemlock. If skin contact occurs, thoroughly wash the affected area with soap and water. While a rash is unlikely, washing helps remove any toxins.
If you suspect ingestion of any part of the plant, or if severe symptoms develop after contact, seek emergency medical attention immediately. Call poison control at 1-800-222-1222 in the United States. Poison control centers are staffed 24/7 by medical professionals. Be prepared to provide information about the amount of plant ingested, the specific part, and the approximate time of exposure. Treatment focuses on supportive care, managing symptoms and cleansing the digestive system.