Can poison oak spread?

A co-worker of mine has poison oak. He just got back from the doctor and the doctor said that it doesn’t spread. It only occurs where you came in contact.

Another co-worker said that yes, it does indeed spread. He swears (since he’s had it so many times that he is an expert on the subject) that when you itch it, anywhere else you scratch the rash will appear. He also stated that everyone else in the house could get it if he didn’t wash the infected clothes.

I think that I would trust a man that went through several years of medical school over a simple technician.

The doctor is right, but your co-worker has a few correct details. Once it bonds with the skin, urushiol (active ingredient at work here) can’t be spread. The itching/rash doesn’t appear until this has happened, so by the time a doctor could diagnose it, the affected area won’t spread. Itching it will not spread it, and if the skin breaks, the fluid coming out won’t contain any urushiol either (it’s intercellular fluid, according to my doctor).

However, it doesn’t bond with clothing as with skin, and it takes a very long time to break down (many weeks potentially). Also, it can spread on the skin before irritation begins – within the first 12-48 hours of contact. So clothing does need to be washed, and the body should be washed (preferably using a remover such as Tecnu) as soon as possible after contact.

Poison oak is very closely related to poison ivy (Rhus radicans). Both plants have a dermatalogically toxic oil in teh plant parts that results in the itchy rash. Only the oils from the plant can cause the rash.

The oils can remain viable on clothing and pets for a long time (I seem to remember a term of up to 6 months on some clothing being taught in Forestry school). However, once the oils are washed off the skin, the resulting blisters CAN NOT cause further rashes.

The best way to avoid developing a poison ivy rash is to wash the affected area with soap and water within 15 minutes of contact. This washes the oils off the skin before the skin can react to it. However, if you were to wash the oils off, then put the same article of clothing on again (the ones with the poison oils on them), a rash would develop. The same would happen if you were to pet Fido after he went browsing through the poison ivy patch.

I’ve been in forestry for almost 10 years now, and have never had poison ivy, thanks to diligent washing.

Hope this helps.

A Google search will tell you everything you want to know about poison ivy. A few months ago I had an itching desire (heh, heh, get it…) to find out about poison ivy, and what I recall about the spreading issue is that once you come in contact with poison ivy the urushiol oil that causes the problem bonds to the skin within 20-30 minutes and after that it will not spread. However if it is on your clothes or garden implements it won’t bond, so you can reinfect yourself long after the initial contact.

Other interesting facts:

  • All parts of the plant contain the evil urushiol. Even the smoke from burning poison ivy contains urushiol.

  • Only humans and a few higher order primates are allergic to poison ivy, so its toxicity doesn’t seem to have any biological advantage.

  • The best home treatment once the itching begins is hot water. Just place it wherever it itches for 30 seconds or so and it will take care of the itching for several hours.

  • Cashews and pistachio nuts are part of the same family and can exacerbate the rash in certain individuals.

Leading to truly horrific respiratory problems for some wildfire firefighters I’ve met. :frowning: