Poison Ivy & Poison Oak

Poison Ivy

There are three native American plants that collectively may be called poison ivy: poison ivy, poison oak, & poison sumac.

These plants can cause an allergic reaction in nearly 85 percent of the population. To be allergic to poison ivy, you must first be “sensitized” to the oils. This means that next time there is contact with the plant, a rash may occur.

Reference: Poison Ivy, Yale University School of Medicine. Yale Medical Group, PO Box 9805, New Haven, CT 06536-0805 (Revised: October 28, 2005)

What Causes an Allergic Reaction?

The resin in the plants contains an oily substance called urushiol. Urushiol is easily transferred from the plants to other objects, including toys, garments, tools, and animals. This chemical can remain active for a year or longer. It is important to know that the oils can also be transferred from clothing, pets, and can be present in the smoke from a burning plant.

What are the Symptoms of Poison Ivy/Poison Oak?

The following are the most common symptoms of poison ivy. However, each individual may experience symptoms differently. Symptoms may include:

  • a contact dermatitis rash characterized by bumps and blisters that itch
  • swelling in the area of contact sometimes occurs
  • blisters that eventually break open, ooze, and then crust over

The symptoms of poison ivy may resemble other skin conditions. Always consult your physician for a diagnosis.

Did You Know?
Scratching poison ivy blisters will not spread the rash. In addition, the poison ivy rash is not contagious—only urushiol (oil found in the sap of poison ivy) can cause a reaction.

Treatment for Poison Ivy/Poison Oak

Specific treatment for poison ivy/poison oak will be determined by your physician based on:

  • Your age, overall health, and medical history
  • The extent of the condition
  • Your tolerance for specific medications, procedures, or therapies
  • Expectations for the course of the condition
  • Your opinion or preference

Making sure you avoid the poisonous plants is the best treatment. It is important to teach your family members what the plants look like and not to touch them.

If contact with the plants has already occurred, you should remove the oils from the skin as soon as possible. Cleansing with an ordinary soap within six hours after the initial exposure has proven to be effective. Repeat the cleaning with the soap three times. There are also alcohol-based wipes that help remove the oils. Wash all clothes and shoes also, because the oils can remain on these.

If the blisters and rash are on the face, near the genitals, or all over the body, your physician should be notified. After a medical history and physical examination, your physician may prescribe a steroid cream, oral steroids, or steroid injections to help with the swelling and itching, depending upon the severity of the rash.

Is Poison Ivy/Poison Oak Contagious?

Poison ivy/poison oak cannot be spread from person to person by touching the blisters, or from the fluid inside the blisters. It can be spread, however, if the oils remain on the skin, clothes, or shoes. This is why washing your hands, clothes, and shoes as soon as possible is very important.

Preventing Poison Ivy/Poison Oak

  • Teach all family members to recognize the plants
  • Make sure you wear long pants and long sleeves when poison ivy or poison oak are in the vicinity
  • Wash all clothes and shoes immediately after you have been outside
  • Make sure you do not touch a pet that might have been in contact with a poisonous plant
  • Wash your hands thoroughly

Poison Ivy on Steroids!

If you’ve noticed anything different about the poison ivy you encounter while hiking or working on a trail, you’re not dreaming. Reports issued published in 2007 document increases in:

  • Poison ivy growth
  • The average size of poison ivy leaves
  • The potency of urushiol oil in poison ivy

Further, each of the separate studies quoted in the New York Times article1 point to the same culprit as the responsible agent for these issues.

The Noxious Weed

Poison ivy plants—the stem and leaf size as well as the amount of oil (urushiol) in them—have significantly increased in average size since the 1950s. According to a study published in Weed Science:

After about eight months, leaf size, stem length and weight and oil content of the plants raised at current carbon-dioxide levels were, on average, 50 percent to 75 percent higher than the plants under the 1950’s conditions, according to the study … Not only did the higher CO2 level double the growth rate, but it made for hardier plants that recovered more quickly from the ravages of grazing animals.2


Study results don’t appear to be conclusive as yet, but a Duke University3 study points to the probability of increased potency of the urushiol oil, to which most of us are allergic, within the past decade.

Not Steroids: CO2

Despite my pathetic attempt to write an attention-grabbing title slug for this article, steroids are not responsible for these issues. Rather, the studies presented so far point to the increase in atmospheric CO2 and its ability to stimulate growth in poison ivy, poison oak, poison sumac, and other weeds commonly found in both Europe and North America. Of course, rising CO2 levels are also attributed to the phenomena of global warming.


Poison Ivy, Now With Stronger Poison by Mike Nizza, The Lede (New York Times), June 27, 2007

Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2, Jacqueline E. Mohan, Lewis H. Ziska, William H. Schlesinger, Richard B. Thomas, Richard C. Sicher, Kate George, and James S. Clark. Contributed by William H. Schlesinger, April 22, 2006

Rising Atmospheric Carbon Dioxide and Potential Impacts on the Growth and Toxicity of Poison Ivy (Toxicodendron Radicans), L.H. Ziska, R.C. Sicher, K. George, and J.E. Mohan, Weed Science, Volume 55, Issue 4 (July 2007) pp. 288–292 DOI: 10.1614/WS-06-190

The information in this article does not substitute for advice or information provided by your physician. In addition, please consult your physician for further information on specific medical conditions or symptoms that you may have.

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