Medical Mythbusters – Poison Ivy!

poison ivy

rashes caused by poison ivy

Now that we are in the dog days of summer, an old friend is rearing it’s ugly, leafy head.  Yes, it’s poison ivy season, my friends, and while most of us think we know all there is to know about this itch-inducing plant, there are some medical myths lurking around it that need to be busted!

First, the facts:  Poison ivy, poison oak, and poison sumac plants are all coated with a colorless oil called urushiol.  Urushiol is a very sticky, colorless substance present in the leaves, stems, fruit, and roots of the plant. After contact with urushiol, about half of us will develop intense itching, swelling, and skin redness. Then, we will develop fluid-filled blisters that are often arranged in a line or streak.  (See photos)  The symptoms are usually most severe within 1 to 14 days after exposure to the plant, but can occur up to 21 days after exposure if someone had never been exposed to urushiol before.

Technically speaking, poison ivy usually resolves within 1-3 weeks without treatment, but without something to control the itching they will be the longest 3 weeks of your life.  Cool wet compresses can be placed on the affected areas for 15 to 30 minutes at a time.  A group of medications called antihistamines are very good at reducing the itching: diphenydramine (Benadryl) is good for night time because it makes you sleepy and loratadine (Claritin) and cetirizine (Zyrtec) are good for daytime because they don’t.  Oatmeal baths, calamine lotion and hydrocortisone cream are also sometimes helpful, but the best way to knock out the rash and itching is to see your primary health care provider to get a prescription steroid treatment.  Sometimes you can get by with just a shot, but that often does’t last long enough (1-2 days) so you can take a course of pills over a couple of weeks.

Now, on to the myth…

TRUE OR FALSE: Poison Ivy is contagious


Poison ivy is not contagious and can not be passed from person to person.  Only contact with urushiol will cause someone else to get poison ivy – the fluid that leaks from blisters does not contain the oil and can not cause symptoms.  Once you’ve washed the urushiol off of your skin (and clothes and fingernails and gardening tools and pets…) you can not spread poison ivy to someone else or yourself.  The rash sometimes appears to be “spreading” from one part of the body to another, but this is because blisters develop at different rates in different parts of the body – any real spreading that went on happened before you realized you had the urushiol on your skin.  This explains why poison ivy has such an unfortunate predilection for our privates.  Please believe me – if you’ve been weeding in the yard, or camping in the woods, make sure you wash your hands before you go to the bathroom as well as after…

John Vaughn, MD – Student Life Student Health Services

Updated by Maribeth Mulholland, MD – Student Life Student Health Services

7 thoughts on “Medical Mythbusters – Poison Ivy!

  1. I got poison ivy on my feet cleaning up weeds around a friend’s lake and I have had it for three months. I was wearing sandals so the rash is in wide stripes across the tops of my feet. I contracted it in July and it is now October. I used Benadryl spray, calamine lotion, and lots of alcohol, but nothing was working so for a few weeks I switched to Lotrimin, thinking it warranted something more drastic. That seemed very good and a few days ago the was nearly completely gone and my skin looked rather normal. Then overnight it rebounded on me. The rash now looks and feels like it did three months ago. what did I do wrong? What can I try next?

    • Lesions may present up to 21 days after exposure to poison ivy in previously unexposed individuals. The rash spontaneously resolves in 1-3 weeks. Soothing creams are recommended for therapy, such as Calamine lotion. While you would think that alcohol would aid the drying of the lesions, it may instead irritate the skin. It is possible that you are being re-exposed due to ongoing contact with contaminated clothing, pets or garden tools. The next step is to see a medical provider to make sure that the rash is not a secondary bacterial infection, and to have appropriate therapy prescribed.

    • I think you were on the right track with the Lotrimin. I too thought I had poison ivy on my toes and did my normal routine for a couple weeks. After it did not go away I looked into foot fungus. But nothing seemed to really work there either. It took nearly 9 months for it to be gone. Here are the things I tried and will do again if/when it comes back. I may go see a doctor too.

      Wash all socks and only wear 100% cotton or wool. No Synthetics.
      Change socks frequently (at least 2x/day)
      Buy a pair of shoes 1/2 size bigger (toss out the old ones)
      Use Lotrimin 2x per day
      Clean shower/tub thoroughly after each use. I did this primarily so others would not get infected. But I’m sure it would help reduce the probability of reinfection.

      Not sure if the below helped but did it anyway:
      Soak feet in warm water and vinegar
      While in shower urinate on foot.

    • I second Technu. Within seconds of using the scrub and then the anti itch spray, the itching was completely gone.

  2. I had a poison ivy outbreak after wearing sandals in a wooded area. It only got worse…and according to my doc, what I had NOT done that was important was wash my sandals which still contained the urushiol oil on them. Wash everything..clothes, bedding… anything which was touched by the poison.

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