What are poison oak, ivy, and sumac?
Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. The result is an itchy, red rash with bumps or blisters. These three poisonous plants can be found in most areas of the U.S., except Alaska, Hawaii, and the deserts of the Southwest. The species can be found growing in fields, wooded areas, on the roadside, and along riverbanks - as well as in urban areas, such as parks or backyards.
The symptoms of these three poisonous plant reactions are similar because they all contain the same chemical: urushiol. Symptoms generally occur in the following phases:
Redness and itching of the skin
A rash erupts on the skin, often in a pattern of streaks from where the plant has come into contact with the skin
The rash develops into red bumps, called papules, or large, oozing blisters
How can I identify each plant?
Poison Ivy: (Toxicodendron radicans) can be identified by their pointed leaves that hang from the stem in groups of three and change color with the season. In the spring, the leaves are green to red, in the summer light to dark green, and in the fall red to bright yellow. A North American flowering plant, poison ivy is found across the east coast of the United States and into Canada.
Poison Oak: (Toxicodendron diversilobum) leaves also cluster in sets of three. The three leaflets have scalloped edges, resembling those of an oak tree, and evolve in color from bright green, yellow-green, bronze or red as the seasons progress. In the winter and spring the plants can produce green, white, or tan berries. In the United States, poison oak is found all along the west coast as a vine (“Pacific/Western Poison Oak” & subspecies) and the southeast coast as a low shrub (“Atlantic Poison Oak”); it is also be found in British Columbia, Canada, as a wine or shrub.
Poison Sumac: (Toxicodendron vernix) thrives only in water and is usually found in swampy or boggy areas where it grows as small trees or tall shrubs. The reddish stems of this plant bear seven to thirteen leaflets, which throughout most of the year remain green until Fall when they turn yellow-red to red; the plant will produce berries from late fall through winter. This poisonous North American shrub/tree can be found throughout the eastern United States, and is often confused with species of Sumac that are not poisonous (Winged, Staghorn).
Why do I have this awful reaction?
Poison ivy, poison oak, and poison sumac are plants that contain an irritating, oily sap called urushiol. Urushiol triggers an allergic reaction when it comes into contact with the dermis, resulting in an itchy rash which can appear within hours of exposure or up to several days later. The rash itself is a form of allergic contact dermatitis - more specifically "Urushiol-Induced Contact Dermatitis" (AKA Toxicodendron dermatitis). Poison ivy, oak, and sumac are three of the most common causes of allergic contact dermatitis in North America.
A person can also be exposed to urushiol in two ways: by direct contact (touching the plant itself) or indirect contact (touching a surface on which urushiol has come into contact - such as a pet's fur, gardening tools, clothing, or other surfaces - which serves as a transfer agent to the skin). Airborne contact is also possible if these plants are burned and the urushiol particles land on the skin, and it can affect the lungs. The first time a person comes in contact with urushiol it is unlikely that a reaction will occur; however, after a few exposures, over 80% of the population will see a reaction every time urushiol makes contact with the dermis (i.e. soaks through the skin and is absorbed by the dermis).
How can I treat these poisonous plant rashes?
Only 15-20% of the global population are immune to urushiol, and an allergic reaction to the poison cannot be cured. However, the symptoms themselves can be treated to make the discomfort as tolerable as possible. Most rashes caused by poison ivy, oak, or sumac are mild and last from five to 12 days – but the timespan depends on how much urushiol a person has been exposed to and how sensitive they are to the toxin. In severe cases, the rash can last for 30 days or longer.
Very hot/very cold showers and epsom salt or oatmeal baths seem to calm skin irritation, in combination with antihistamines and the application of lotions such as calamine, aloe, or anti-itch creams like hydrocortisone, Tecnu or Zanfel (over-the-counter products designed to prevent/provide relief specifically for skin reactions to poisonous plants). Resisting the urge to scratch is also very important to ensure the rash does not get worse or leave any scarring.
Luckily, once the plant oil has been absorbed, the rash is no longer contagious and will not spread to others.
How can I prevent future rashes?
If you are like me and often find yourself in situations where it is difficult to avoid contact with poisonous plants, there are several ways that urushiol rashes can be prevented:
Learn to identify the poisonous plants in your area and practice spotting specimens in the wild (take a photo along with you!).
Be especially cautious in areas where you know poisonous plants grow.
Wear closed shoes, knee socks, long pants, long sleeves, wrist guards, and gloves when spending time in risky areas.
Carry water, hand sanitizer, or products like Tecnu with you in the woods. (I have found that immediately rinsing my hands with water following contact with a poisonous plant can subdue if not eliminate a reaction. Tecnu is also commended for its ability to diminish the presence of urushiol oil.)
Remember that urushiol can be spread to other parts of the body if it has not been entire absorbed yet - so be sure to scrub your hands and under your nails after spending time outside.
Put your clothing straight in the washer when you get home; unabsorbed oil from poisonous plants can stick to objects and remain potent for as long as 5 years!
If you think a pet may have gotten into a poisonous plant, bathe them as soon as possible - and wear rubber gloves! Animals' fur coats protect their skin from urushiol - but the toxin can be transferred from their fur to your hands.
Have more details? Tips for treatment? Questions? I'd love to hear from you! Feel free to share any thoughts in the comments below.
Thank you for reading!
Photo collages made by me; photos gathered from Google Images.