The following is from one of the Tracker mailing lists on the
Internet. It was posted by Kevin Reeve.
There have been many posts on poison ivy, so rather than quoting one, I will
just post what I know.
Poison Ivy is actually caused by an oil called urishal (varied spelling) that is found through out the plant.
It is most heavily concentrated on the leaves, but can be found in the stem and roots
as well. It is also the same poison found in Poison Oak. When this oil comes in contact with the skin, it causes the body's immune
system to release histamines to fight off the attack of the oils. The blistering and itching are basically the immune system going way overboard
to fight this poison.
The best treatment is prevention through awareness. I am so allergic and
have had such bad experiences that I always know where my feet are going. Because ivy can grow as a creeping vine up trees you have to be careful that
you don't brush up against what you thing is an ash tree but that has been taken over by ivy. The leaf shapes can fool you as they are similar.
If you do come in contact, you have some time to get the oil off your skin
before your body reacts. You must use a detergent to break down the oils. I prefer to wash with Dawn dishwasher detergent. I tried using ecosoap and
because it had no detergent, I still got the reaction.
Antihistimines are recommended as well, but once the rash occurs, they are
of little value. Jewelweed is also useful as a preventative if exposed, but I usually wash first then apply jewelweed.
Once you have the rash, it can go systemic. The body senses a bad enough problem that it releases histimines to many sites. This is where it can get
serious. Now you may get blisters popping up where you were never even exposed. The fluid from the blistering is not going to spread the
rash,because it is syrum of the body, not poison. It is like any other serious allergic reaction at this point and anaphalactic shock is a
Once systemic the only treatment that I have found effective is the
administration of steroids, such as cortizone. They basically shut down the immune system response, but they have side affects that can last for a
while. SInce they shut down the immune system, you can be susceptible for some time to disease after taking it. However, if you have ever had
systemic poison oak before, you realize that you will do anything to make it go away.
There is more I could cover, but I am out of time.