IVY IS FULL OF SURPRISES
by Whit Gibbons
April 25, 2004
to the National Park Service, spring is the most likely time for people
to succumb to an age-old ailment of being outdoors-poison ivy. But ecologists,
hunters, and wildlife managers who spend time year-round in swamps and
woods where poison ivy is a common plant, seldom get a serious case of
poison ivy. Maybe they are unconsciously cautious and actually avoid the
plant without being aware of doing so. Also, most people have no reaction
when they casually brush against poison ivy, and 20 to 40 percent are
not sensitive at all. Some people spend their lives around poison ivy
without ever having a reaction.
is an eastern U.S. plant with three leaflets at the end of each stem.
The stem holding the leaflets is usually reddish, and all parts of the
plant--leaves, stem, fruits, and roots--produce an oil that can cause
skin irritation in some people. Any contact of the body with the oils
can cause a problem, whether from patting a dog that has just walked through
poison ivy or touching clothes that have come in contact with the plant.
You can even get a case of poison ivy internally by inhaling oil droplets
that become airborne in smoke when the plants are burned. You can even
get poison ivy in the winter simply by touching the stem, even though
the leaves are gone.
myths, and disagreements about the properties of poison ivy are legion.
You do not spread poison ivy by scratching where it itches, despite what
some people say. New blisters and irritated areas can appear more than
a week after exposure to the oils, but these merely represent the normal
lag time that can occur after initial contact. Also, you cannot give poison
ivy to others, except by bringing them into contact with the oils that
are on your own body or clothes after encountering the plant.
of wildlife can eat poison ivy without being adversely affected. Dozens
of kinds of birds including bobwhite quail eat the fruits, which are clusters
of smooth, white berries that appear in late summer. I know of a serious
case of poison ivy being contracted by a wildlife student who sorted through
the stomach contents of a recently killed deer. Among the data he recorded
for his research on the diet of deer was that they sometimes eat a lot
of poison ivy leaves.
with my favorite dermatologist to find out something about the symptoms
of poison ivy. According to her, the oils cause a contact dermatitis (which
means inflammation of the skin) that cannot be distinguished from one
caused by numerous other plants and products we might come in contact
with. Among the plants known to cause dermatitis that is superficially
similar to that caused by poison ivy are black walnut trees, red cedar,
and fresh okra. However, many, possibly most, people are not affected
by contact with those plants.
irritation--blisters, burning, itching--normally occurs 24 to 48 hours
after contact with any part of a poison ivy plant, and expression of the
ailment follows a bell-shaped curve. The most severe symptoms occur midway
between a 2- to 24-day period. One treatment for relief of the symptoms
of a severe case is a steroid, such as prednisone. The steroid masks the
symptoms even though the body's response to the irritation continues.
My dermatologist cautions that some doctors treat with steroids for too
short a period. Thus if your reaction is following a 24-day cycle and
you take steroids for only 7 days, the symptoms could reappear before
the peak of irritation has been reached.
field guides distinguish between poison ivy and poison oak. Subtle differences
are noted, ones that do not really matter for recognizing the plants.
Both have three leaves and produce the oils that make you itch. Some biologists
claim that poison oak is more virulent than poison ivy. I'm not sure about
that part, but I do suspect that under certain circumstances any of us
can succumb to these three-leaved plants, so watch what you touch when
you are in the woods this spring.
you have an environmental question or comment, email