You try to be careful when you hike in the woods, because you don’t want the itch of poison ivy spoiling your fun. Maybe you are also acquainted with poison oak and poison sumac as well. But did you know there are other plants you may obtain at the grocery store or even grow in your yard that contain the dermatitis causing agent, urushiol? There are a number of them.
Many members of the family of plants called Anacardiaceae contain the dread dermatitis-producing chemical urushiol, as well as related compounds. Some of these will doubtless surprise you, as you may have eaten some of these without suffering harm. First, what is urushiol? Then, what are some examples of urushiol containing plants commonly grown, and why do they seldom pose serious harm?1
What is Urushiol?
Urushiol (from the Japanese “urushi” for a type of lacquer) is not a single compound, but rather is a mixture of closely related compounds, called “catechols,” which also possess a long-chain alkyl group. Urushiol is an oily yellow liquid, which boils at 200 to 210 degrees centigrade. It is the primary cause of the characteristic poison ivy rash. Since it is water-insoluble, it does not readily wash off. For that reason, some try using hot water, which is a mistake, as that opens body pores, allowing more of the oily substance to penetrate the skin and worsen the rash.
What Commonly Grown Plants Contain Urushiol?
Not all plants that contain urushiol are considered undesirable. Some plants deliberately grown on farms, in landscaping, and even in home gardens include cashews, mangoes, pistachios, and Ginkgo bilboa. Each of these plants contains urushiol and related polyphenolic compounds.2 In the case of the cashew, the irritant is found in greatest concentration in the liquid surrounding the cashew nut.3 For the ginkgo bilboa, it is the leaves that contain the chemical. The peel is the culprit in the case of the mango, while the pistachio nut, itself, houses its urushiol.
Why Do These Plants Cause Little Harm?
The cashew is cleaned and roasted, thus destroying any harmful urushiol. The same cure applies to the pistachio. Careful peeling of the mango plus slicing the fruit off the pit does the job for most fans of the delectable fruit, while simply enjoying the eye appeal of the ginkgo bilboa avoids difficulties with it, as well. By taking the proper, minimal precautions, these plants can make a popular addition to your farm, your garden, and/or your next meal (or health supplement).
1 Some individuals may be particularly susceptible to the chemical irritants found in these plants, and should take special precautions to avoid exposure.
2 A phenol is an aromatic ring substituted with a hydroxyl group (-OH); thus, a polyphenolic compound has more than one such group.
3 Actually not a nut, but a seed.
Disclaimer: The author is neither a dietician or a medical practitioner. For health and dietary purposes, seek the advice of the corresponding professional.
Colorado State University – “Secondary Compounds Within the Anacardiaceae,” by Laurel Hartley
Palomar College – “Poison Oak: More Than Just Scratching The Surface,” by WP Armstrong.