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April 25, 2012 at 8:16 PMComments: 0 Faves: 0

Poison Ivy: Myths and Facts

By Jeffrey VanWingen M.D. More Blogs by This Author

Patients come into my office all the time with various rashes.  I see rashes of all sorts: itchy, bumpy, scaly etc.  There is one rash in particular that really gets my dander up—literally.  In fact, just looking at this rash makes me feel itchy.  Which rash am I referring to?  Poison ivy. This rash is making its presence again in my office after a few months of winter dormancy.  This article will examine some facts and myths on this troublesome dermatologic scourge.

“Leaves of three, let it be”

Poison ivy is present throughout North America.  Interestingly, it is not found in Europe or other parts of the world.  Suburbanization has created favorable habitats for poison ivy and it has become more prevalent through the years. 

The plant can exist as a shrub, ground cover, or a climbing vine.  Contrary to its name, it is not a member of the ivy family.  Regardless of its larger scale form, the plant is characterized by its three almond-shaped leaves and its reddish stems.  Different forms of leaves exist with saw-tooth or smooth patterns.  In short, if you come across an ivy plant with three, almond-shaped leaves and reddish stems, don’t touch it!

What’s the “poison” in poison ivy?

The poison ivy plant produces a clear sap or resin called urushiol.  Touching the plant and transferring the urushiol to the skin can produce an intense immune reaction. 

This reaction causes marked inflammation leading to the characteristic rash, which will leave your skin with an unbearable itch.

The dreaded rash

  • Poison ivy rash has the following characteristics:
  • The rash is present wherever the skin has been exposed to the resin. 
  • Typically, resin on the hands transmits to other parts of the body—the face, arms and even the genitals. 
  • Often times, “sweeps” are seen, which are linear marks of the rash.  Due to the intense immune response to the sap, raised redness and blisters develop.

Myth #1: Poison ivy is contagious.

Many people believe that if the blisters pop, the rash will spread, further in the same person or, even to another person.  This is not true.  

Once that sap is removed, no further rash can be produced or transmitted.  The catch here is that it takes a variable amount of time for that rash to manifest, depending on the thickness of the skin.  Thin-skinned areas like the face, genitals or hairless portions of the forearms are the first to see the rash develop. 

Within days, the rash exhibits on thicker-skinned areas, like the palms, scalp, back and bottoms of the feet.  This is what gives the appearance that the rash is spreading.

Myth #2: Some people are immune from poison ivy's rash.

Because poison ivy depends on the immune system to cause the rash, different people have variable responses, but no one is completely immune from developing the rash. 

If you have been exposed to poison ivy in the past, you may actually experience worse symptoms if you develop it again. 

Like other situations regarding allergies, some people are more susceptible than others, but it would be false to say that some people are simply immune from developing the rash.


The most important thing to remember, when treating the rash, is to hinder the immune system's response to the skin’s exposure to the sap.  This is generally accomplished with steroids.  If the rash is localized, just over a small, easy to reach area, a steroid cream can be applied.  If the rash is more extensive, it is best to treat from the inside-out with tablets. 

Those with poison ivy should be advised that a couple pitfalls exist with the oral or tablet form of treatment.  Poison ivy is a fastidious reaction and is present for at least two weeks.  As such, treatment needs to occur for an extended period.  A short course of treatment ended too early, will only cause the rash to re-erupt. 

Additionally, steroids should be used with caution.  If prescribed for more than a week or so, it is wise to taper down the dose before going off the product completely, in order to protect the body’s production of its own steroid hormones.


Obviously, prevention is better than experiencing the rash and the treatment. Avoidance is key and this is best accomplished through knowledge and the ability to identify the plant. 

If exposed, wash immediately with soap and water.  If out and about where there may be poison ivy, cover exposed areas.  Beware that animals can also transmit the sap on their fur.

Be especially cautious if you're in unfamiliar territory, like when you're on a camping trip, or exploring a new area outdoors.


Poison ivy is a common finding among the foliage of North America.  Contact with the plant can expose the skin to its sap which may result in an intense allergic rash. 

The rash evolves from thin to thick-skinned areas, and lasts for at least two weeks.  Treatment is generally approached with steroids, either topical or tablets, depending on the severity of the rash. 

Save yourself from the itch of poison ivy, by educating yourself on what poison ivy looks like, and not leaving your skin exposed in outdoor areas that may have the poison ivy plant.

Photo Credit: Diego3336   Peter Kaminski   Voxphoto

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