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Three Little Leaves: Avoiding and Treating Poison Ivy

Summer is here!  Which means I’ve got another poison oak rash on my arms and legs from a hiking trip to Big Sur.  I am not the only one – the three CVS pharmacies around me are all sold out of Tecnu – the most common treatment for poison ivy and poison oak.  What is a brother to do?  Here’s what my doctor told me:

Well, the first thing I should have done is done a better job avoiding it.   Poison ivy/oak/sumac all have an active ingredient called urushiol that causes an allergic reaction.  Urushiol is an oily compound, so it isn’t going to wash off or rub off easily.  And the tiniest sample of the oil could cause an allergic reaction in hundreds of people.  So if you are going on a hike or summer stroll: the most effective thing you can do to avoid poison ivy is to cover up when going into the woods and wash your clothes thoroughly before you wear them again, as in twice with the washer set on “hot”.  It isn’t really realistic for you to try to spot all of the poison ivy/oak/sumac around you while you are walking around.  While avoiding every plant with three leaves is a good start, the vines, trunks and sprouts of these plants can also cause the rash.  Oh, and one more thing, poison sumac has 3, 5 or 7 leaves.  Best of luck trying to avoid that one.

Once you’ve been exposed.  All that you can hope to do is damage control.  There is a lot of mythology about treating poison ivy, but let me lay out the facts to try to illustrate how hopeless “treating” it can be.  The tell-tale rash is going to come out between 1-14 days after exposure, or for a first exposure – up to 21 days after.  So you might have rashes developing all over your body because you think you are “spreading it”, but it is probably just a result of a delayed outbreak.  Spreading poison ivy is actually hard to do, only if you actively scratch the rash and get the oil under your finger nails can you realistically spread the urushiol.  With this in mind, if you think you have been exposed to poison ivy, do the following:

1)  Buy Tecnu and follow the instructions to cleanse your skin

2) Give your clothing a 2x run through the washer on hot

3)  Take antihistamines (Allegra, Claritin, Benadryl) to releve the itching (assuming you have no adverse reactions to antihistamines)

4)  Use calamine lotion or steroid creams (hydrocortisone) to relieve the itching in the first few days after an outbreak

5)  If all else fails and you are getting rashes on the bottoms of your feet, hands and everywhere, go to the doctor.  They will prescribe you steroid pills (prednisone) that will make your itching and rash abate almost immediately.

Happy summer.

(Photo credit:

2 Comments Post a comment
  1. Emily #

    I suspect that even for those of us who are not allergic to poison oak can become allergic if environmental factors are compounded.

    A week after a hiking trip I started developing rashes near or on bug bites that had long healed. I thought they were fresh bites, but given the progression of the rashes, they seem like allergic reactions to poison oak. My suspicion is that while the lipid content and thickness of my epithelial layers prevented most of the poison oak from penetrating, there were definitely pinpoint spots on my leg that were compromised – mainly because a mosquito or horse fly had bitten me. I also fell on my left leg at one point, scraping myself against the bark of a fallen log. This leg has by far fared the worst from my first ever poison oak reaction. Thanks to newtome for this blog posting.

    May 22, 2011
    • newtome #

      Hey, thanks for the insight!

      May 22, 2011

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