Beyond a supervillain in a DC comic, Toxicodendron radicans (Gillis, 1971), better known as poison ivy, acts as the infamous culprit behind many hives, redness, and rashes. Commonly found along heavily wooded forests and wetlands, this distinguishable plant is considered “early successional”, which means it prospers in areas with activity and thrives in disturbance opposed to isolation, unlike other native plants (Fitch & Kettle, 1948). Indigenous to Asia and North America, poison ivy ranges from a glossy to a fuzzy-like appearance, but can still be identified by its sharp compound leaves consisting of three leaflets along a thin, brown stem.
Responsible for being North America’s most common allergen behind allergic contact dermatitis (Gladman, 2023), the population of poison ivy has been congruent to rising climate change patterns. With the recent increase of carbon dioxide production, the rate at which vines are photosynthesizing are at an all-time high. This results in the plant being more responsive to photosynthesis and generating a higher production of urushiol, one of the main irritant constituents of the Toxicodendron species (Tao, et al., 2023). This phenolic lipid works by binding to the proteins within the membrane of the epidermis, hindering their communicative ability. This ignites a process known as cell-mediated immune response, affirming that symptoms are not from plant’s contact but instead the immune system attacking itself as seen in Figure 1 (Barrat, 2014). This substantiates why symptoms are often 2-3 days delayed (Monroe, 2020), and refutes the common belief that repeated exposure constitutes immunity. Despite its outwardly conspicuous threats, poison ivy proves to have more purpose than it seems.
Figure 1: 50-year old man after handling a dead poison ivy plant, resulting in a reaction comprising of vesiculations in a linear configuration (Monroe, 2020).
Throughout history, the hazardous nature of this unforgiving plant poses many questions regarding human safety, with proposed ideas including that of chemical warfare and infliction of harm. With the introduction of many powerful toxins in World War 1, speculation regarding urushiol-filled artillery grenades arose, with the American Chemical Warfare Service wanting an effective toxicant similar to mustard gas or lewisite (Mohan, 2006). Explosive devices and shrapnel were intended to release the dangerous aerosol when emancipated, as well as leave a deleterious injury upon contact. Over the course of World War 2, many toxins were implemented in America’s biological programs. Small four-pound aircraft bombs were created and tested, consisting of varying states of this toxin, such as being dissolved in an aqueous solution or ground to a fine powder (Pitschmann & Hon, 2016).
Since the discovery of poison ivy, its distinct features and noxious chemical properties have expanded our knowledge on climate change, the immune system, and historical conflicts. Through exploring and repurposing urushiol, we can further advance not only what we know about science, but the origins of this unique plant.
References:
Barrat, J., 2014. A Poison Ivy Primer, Smithsonian Institution. Available at: <https://www.si.edu/stories/poison-ivy-primer#:~:text=Scientists%20 speculate%20 urushiol%20 evolved%20as,as%20a%20 defense%20against%20 people> [Accessed 28 October 2023]
Fitch, H.S. and Kettle, W.D., 1983. Ecological succession in vegetation and small mammal populations on a natural area of northeastern Kansas. Proceedings of the North American Prairie Conference, 7, pp.117-121.
Gillis, W.T., 1971. The systematics and ecology of poison-ivy and the poison-oaks (Toxicodendron, Anacardiaceae). Rhodora, [online] 73(793), pp.72–159. Available at: <https://www.jstor.org/stable/23311349>
Gladman, A.C., 2006. Toxicodendron dermatitis: Poison ivy, oak, and sumac. Wilderness & Environmental Medicine, [online] 17(2), pp.120–128. https://doi.org/10.1580/PR31-05.1.
Mohan, J.E., Ziska, L.H., Schlesinger, W.H., Thomas, R.B., Sicher, R.C., George, K. and Clark, J.S., 2006. Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO₂. Proceedings of the National Academy of Sciences of the United States of America, [online] 103(24), pp.9086–9089. Available at: <https://www.jstor.org/stable/30051901>
Monroe, J. (2020) Toxicodendron contact dermatitis: A case report and brief review, The Journal of Clinical and Aesthetic Dermatology. 13(9 Suppl 1):S29-S34.
Pitschmann, V. and Hon, Z., 2016. Military importance of natural toxins and their analogs. Molecules, [online] 21(5), p.556. https://doi.org/10.3390/molecules21050556.