Poisonous Plants

  • Poison ivy is a common US plant most prevalent in Eastern regions of the country. “Leaves of three, let it be,” is a good rule of thumb, as a hallmark sign of the plant is clusters of three broad leaves on vines or shrubs that can be climbing vertically or laying low to the ground. The leaves are usually green but can show tinges of red and orange during different seasons.

  • Poison oak is similar to poison ivy, although it is more prevalent in the Western and Southern regions of the United States. It too grows in leaves of three, but has curvier leaves than poison ivy similar to those of an oak tree and grows in the form of a vine.

  • Poison sumac deviates from the three-leaf pattern, having as many as a dozen leaves on a single branch. The plant takes the shape of a shrub, and often features small yellow flowers that turn into berries.

  • Poison ivy, oak and sumac plants release the oil, urushiol, which may cause allergic eczematous contact dermatitis characterized by redness, swelling, papules, vesicles, blisters and streaking. This rash may not show up immediately, sometimes taking a week after contact to appear. It is not contagious, and can only be caused by coming into contact with urushiol.

  • Thoroughly washing the exposed areas within about ten minutes of contact may prevent urushiol contact dermatitis from occurring. Otherwise, calamine lotion and cortisone cream will help treat urushiol-induced rashes. Cold compresses and antihistamines can provide relief from itching and painful blisters.

  • The extent of the allergic reaction differs based on individual sensitivity to urushiol. Approximately 15% to 30% of people do not have an immune response to the oil, whereas at least 25% have a strong response that results in severe symptoms. Rashes affecting the eyes, face or genitals may require visit to a physician, who might prescribe a corticosteroid such as prednisone.

  • Another plant that causes skin irritation is wild parsnip. Its stems and leaves contain psoralens, a chemical that causes phytophotodermatitis. Skin that comes into contact with the psoralens from wild parsnip and is then exposed to sunlight can become burned and blistered. Keep these areas clean, dry and out of the sun, and apply antibiotics and bandages regularly.

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    While ragweed is notorious for causing hayfever allergies, the widespread plant can also cause a rash consisting of small, itchy bumps and blisters for certain people who touch the erect, clumped stems. Itching can be controlled with OTC anti-itch creams, such as hydrocortisone.

  • Although the root of a stinging nettle can actually be used for medicinal purposes, the hairs that cover the leaves and stems can prick the skin and release several chemicals, including acetylcholine, histamine and formic acid. While ultimately harmless, the stings can be relieved with a thorough wash followed by antihistamines, calamine lotion or hydrocortisone cream.

  • Secretions from poisonous plants can be spread in indirect ways, too. Wear gloves and clean any clothing or items that you suspect is covered with an irritant, and wash pets that you think may have come in contact with poisonous plants. Although pets may not be directly susceptible, they can rub against your skin and cause a reaction.

  • Never burn poisonous plants in an attempt to get rid of them. The chemicals can become airborne, and cause severe reactions in the mouth, eyes, nasal passages and lungs, not just the skin.

  • To protect your skin from the variety of poisonous plants commonly found in the American wilderness, take a few precautions. Wear long pants, long sleeves and closed shoes. Have water readily available for cleansing, and wear a barrier cream if you know you will be near certain plants.

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There are still a few more weeks of summer left, and your patients are spending time outdoors enjoying hikes, cookouts and camping trips. But exploring nature is not always a walk in the park. Advise your patients to avoid the poisonous plants in this slideshow.

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