I know what you are thinking…….he’s blogging about another rash!  I think this one though is an important one to recognize and treat.  Besides, so many of you have said to me “I’m really bad at rashes!”

What do you think this rash is?  What characteristics of this rash make it readily identifiable?  If you saw this patient what specific questions would you ask?  How would you treat it?

This is a classic rash of poison ivy (oak or sumac.)  The key features of this rash are seen in the photo above.  The rash has a vesicular and component.  Another key feature is the areas of linearity and “crisscrossing.”  The rash usually develops within 24 to 48 hours after exposure.  Contrary to popular belief, the vesicular fluid contains no antigen and is not responsible for spreading the rash.

If someone is exposed to poison ivy, they should immediately irrigate the area.  It should be noted that at 10 minutes after exposure, only 50% can’t be removed.  This decreases with additional time up to 30 minutes when all of the oil is absorbed.

There are several over-the-counter products available for post exposure prevention of the rash.  Tecnu and Zanfel have demonstrated promising results but the number of subjects studied was low (n=20 and 24 respectively.)

When the patients present with poison ivy, treatment is directed at control of pruitis and limiting the duration of symptoms.  There are many over-the-counter products available for control of pruritis.   Tepid baths with baking soda or colloidal oatmeal, cool compresses, and calamine lotion are common effective treatments.  Oral antihistamines such as benadryl or atarax is also effective.

The mainstay of treatment for moderate or severe poison ivy is systemic steroids.  When the poison ivy becomes significant enough to require steroids ( I tend to use more than one body part as my gauge,) the risks of application of topical steroids outweighs the benefits.  The most common mistake I see with poison ivy treatment is giving too short a course of prednisone.  The suggested length of treatment is 10 to 12 days.  The taper I use is as follows:

Days 1-3: 60mg qd

Days 4-6:  40mg qd

Days 7-9:  20mg qd

Days 10-12:  10mg qd

To summarize, we will be seeing patients in the coming weeks with poison ivy as the weather is getting nicer.  The rash is easy to identify in most cases with history of exposure.  Remember that the rash will usually be linear in places and will usually have vesicles present at some point.  Make sure you recommend symptomatic control and extend your steroid taper to 10-12 days.

I have included two articles to review in case you’d like to read more on the topic.


  1. Gladman, A.  Toxicodendron Dermatitis:  Poison ivy, Oak, and Sumac.  Wilderness and Environmental Medicine. 17 (2006)120-128
  2. Sasseville, D.  Clinical Patterns of Phytodermatitis.  Dermatology Clinics. 27 (2009) 299-308


8 thoughts on “

  1. Don,

    Is a taper necessary? I usually give a burst of 60 mg per day for what ever time frame I am using. Perhaps we could have a discussion about taper vs. burst.


    1. I’ve always heard it was. I’ve taken care of more than a few who come to the ER after being placed on a shorter course. What do others think?

      1. I think that the two of you may be making two distinct, yet correct points.

        With respect to Craig’s comment, there is literature to suggest that you can burst for 2 weeks without necessitating a taper. I also agree with Don that these folks (and I’d probably include most contact dermatitis here) need more than the typical “COPD burst” of 5 days. However, saying that they need 10-14 days of systemic steroids isn’t necessarily the same as saying that they need a taper.

        Interested to hear others’ thoughts on this.

  2. Don’t forget to ask if the rash is on their penis. This is a dead give away for men as they spread the oils everywhere they touch. I find it is only reliable in about 50% of women…in Vegas that is.

  3. Alternatively, rather than a 2 week course, you can also use a one time IM dose of Kenalog (40 mg). This is much easier and obviously negates the issue of compliance. As for taper or not, everything I have read states that the longer course is necessary in order to prevent a rebound of the rash/sypmtoms. I have not seen anyone return for a rebound after a shorter course, but then again, most of us treat with the longer course. This is another reason I favor the IM kenalog dose.

    1. IM Kenalog? this is new to me, sounds like a great option. Is this to be given local to the rash or just IM anywhere? Is someone actualy using this? Results?

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