Subject: Poison Ivy - FAQ/Info needed

From: [email-masked] (Paul Hunter)
Date: Fri, 2 Jun 1995 14:48:08 GMT

I am looking for information on poison ivy. Would someone pls point me to a FAQ
or other source of info.

Of particular interest is info on the growing season, how to get rid of it,
whether young plants are more potent than older plants, treatments, how to
build a tolerance (if possible), affects on dogs etc.

Thx

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From: Scott Ranger <[email-masked]>
Date: 5 Jun 1995 01:30:58 GMT

I can't offer any literature help for you, but years of field experience 
has taught me a few things.

The active ingredient for the "poison" is urhusiol, a rather unvolatile 
oil contained in the sap of the plant.  The same chemical is found in all 
poisonous species of the genus Rhus (=Toxicodendron), as well as the 
Florida poison tree (Metopium toxiferum).  Since the chemical doesn't 
change, the toxicity of the plant does not vary other than with times of 
very active sap movement and plant growth.

A large number of poison oak/ivy cases occur in the early spring when not 
much more than stems are out, but the sap is rising and thus available to 
reach skin when stems are bruised.  Young leaves are more fragile and 
thus the oil is more easily tranismitted to skin.  People do not 
recognize the stems since most only look for "leaflets three, let it be."

Dogs and cats are a problem, because as they wander the woods, they 
easily pick up the oil on their coats (generally preventing their 
dermatitis) and transmit it to humans when they pet the animal.

The growing season varies with the local climate.  Here in Georgia (USA), 
the winter stick phase is very apparent in January/February and the first 
flush of leaves come as early  as late February in south GA and early 
March in north GA.  Further north it will leaf out later.

This chemical is found to some degree in just about every species in the 
Anacardiaceae, the sumac family.  Some people get dermatitis from cashew 
nuts!  

There are some drugs that claim to offer resitance.  I have no experience 
with them and cannot comment, but I'm very skeptical.  Many years of 
stomping in the fields and woods and I've only gotten poison ivy from my 
own yard doing gardening!  A watchful eye is the best prevention!

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From: [email-masked] (K. R. Robertson)
Date: Tue, 06 Jun 1995 08:32:36 -0600

Here is a bit of information about poison ivy from a handout that I use. 
There is a good publication on poison ivy available for a few dollars:

		Glen S. Winterringer. 1963. Poison ivy and poison sumac. Illinois State
Museum, Story of Illinois series, No 13. 36 pages.  Address: Publications
Office, Illinois State Museum, Spring and Edwards, Springfield, IL 62706.

There was also a good article about poison ivy in Smithsonian several years
ago.  I don't have the month or year, but the article is "Science has got
its hands on poison ivy, oak and sumac" by Noel Vietmeyer.  I can mail you
a copy if you want.

	1.	Poison-ivy (Rhus radicans) belongs to the sumac family (Anacardiaceae),
along with staghorn sumac and its close relatives: pistacio, cashew, mango,
squawbush, poison-sumac, and some poisonous trees of the tropics.  It is
not closely related to Boston-ivy nor English-ivy.
	2.	Some poisonous relatives of poison-ivy are poison-sumac (Rhus vernix),
poison-wood (Metopium), and guao or maiden-plum (Comocladia) of the
Caribbean area, cashew nut (Anacardium occidentale), Dhobi-nut
(Semecarpus), and the mango (Mangifera).  In mango, the poison is in the
pedicel and possibly in the skin of the fruit.
	3.	Poison-oak is not an oak, but a sumac.  It is called poison-oak because
its leaflets resemble the leaves of some native oaks.
	4.	There is no poison-oak in Illinois; elsewhere there are two species
with this common name: one in the southeastern United States (Rhus
toxicodendron) and one along the Pacific Coast (Rhus diversilobum).
	5.	The chemical nature of the poison in poison-sumac and in the poison-oak
species presumably is related chemically to that in poison-ivy, but its
actual identity has yet to be determined.  It is possible that the human
body can detect differences between these poisons, but this has yet to be
demonstrated.  It is likely that a person who is ÒallergicÓ to one of these
plants is likely to be allergic to them all.
	6.	The poisons are not volatile and therefore cannot be contracted  Òout
of the air.Ó  A direct or secondary contact is necessary.
	7.	The poison may be spread in the smoke of burning poison-ivy because of
tiny droplets of the poison present on the particles of dust and ash in the
smoke.
	8.	Poison-ivy may be spread by animals.  Petting a dog following its
having run through a patch of poison-ivy is a frequent way of contracting
poison-ivy.
	9.	Poison-ivy may be spread by articles of clothing.  A person may
reinfect himself by handling the same shoes he wore when he walked through
a patch of poison-ivy.
	10.	The poison cannot be spread by breaking blisters on the skin.
	11.	There is little way of hastening the departure of the disease.  Any
medicines that are used on the skin serve to help dry the blisters, treat
for secondary infection, or relieve itching.  ACTH or cortisone derivatives
will help cure the disease, but they should be administered only with the
advice and direction of a physician.
	12.	The level of sensitivity differs from person to person.  Once one has
surpassed his threshold of sensitivity, he will most likely alter that
threshold.  In some cases, it appears that a severe case will herald more
severe cases; in others, it appears that one very virulent case precludes
any others.
	13.	The initial contact is sufficient to give a person a rash if he is
sufficiently sensitive.  Normally, however, one must be sensitized by an
initial contact before the sensitivity develops.
	14.	Washing with strong soap merely removes excess poison from the skin,
but will not remove any which has already reacted, because the poison is
believed to form a complex with skin proteins and therefore is not
removable short of removing the skin!  Even so, it is difficult to wash off
this insoluble poison completely.
	15.	Eating a leaf of poison-ivy may have disastrous results.  One may
surpass his normal level of immunity by the first bite; in this case he is
in for an internal case of poison-ivy, occasionally known to be fatal.
	16.	Injections are sporadic in effectiveness.  They should generally be
avoided as prophylactic measures, and definitely should be avoided during
an attack of the dermatitis.  At best, they may confer some degree of
immunity; at worst, they may make a mildly sensitive person very sensitive.

	17.	The mechanism of sensitivity is not thoroughly understood.  It does
not behave like protein sensitivities such as hay fever.  It is a
hypersensitivity of the delayed type, whose mechanism is related to that of
organ transplant rejection.
	18.	There are some persons who appear to be immune to poison-ivy. 
Probably very few are totally immune, but rather have a high threshold of
sensitivity.  Any survey of the population generally reveals about 50% of
those surveyed are immune at the time of census.
	19.	There is no known easy method for getting rid of poison-ivy, either
the plant or the disease.

Originally prepared by William T. Gillis, 1973
Revised by Kenneth R. Robertson, 1993, Illinois Natural History Survey