http://www.fda.gov/fdac/features/796_ivy.html (page is no longer found)
"Poison oak, ivy and sumac are very fragile plants," says William L.
Epstein, M.D., professor of dermatology, University of California, San
Francisco. Stems or leaves broken by the wind or animals, and even the tiny
holes made by chewing insects, can release urushiol.
Reactions, treatments and preventive measures are the same for all three
poison plants. Avoiding direct contact with the plants reduces the risk but
doesn't guarantee against a reaction. Urushiol can stick to pets, garden
tools, balls, or anything it comes in contact with. If the urushiol isn't
washed off those objects or animals, just touching them--for example,
picking up a ball or petting a dog--could cause a reaction in a susceptible
person. (Animals, except for a few higher primates, are not sensitive to
Urushiol that's rubbed off the plants onto other things can remain potent
for years, depending on the environment. If the contaminated object is in a
dry environment, the potency of the urushiol can last for decades, says
Epstein. Even if the environment is warm and moist, the urushiol could still
cause a reaction a year later.
"One of the stories I tell people is of the hunter who gets poison oak on
his hunting coat," says Epstein. "He puts it on a year later to go hunting
and gets a rash [from the urushiol still on the coat]."
Almost all parts of the body are vulnerable to the sticky urushiol,
producing the characteristic linear (in a line) rash. Because the urushiol
must penetrate the skin to cause a reaction, places where the skin is thick,
such as the soles of the feet and the palms of the hands, are less sensitive
to the sap than areas where the skin is thinner. The severity of the
reaction may also depend on how big a dose of urushiol the person got.
Quick Action Needed
Because urushiol can penetrate the skin within minutes, there's no time
to waste if you know you've been exposed. "The earlier you cleanse the skin,
the greater the chance that you can remove the urushiol before it gets
attached to the skin," says Hon-Sum Ko, M.D., an allergist and immunologist
with FDA's Center for Drug Evaluation and Research. Cleansing may not stop
the initial outbreak of the rash if more than 10 minutes has elapsed, but it
can help prevent further spread.
If you've been exposed to poison ivy, oak or sumac, if possible, stay
outdoors until you complete the first two steps:
|First, Epstein says, cleanse exposed skin with generous amounts of
isopropyl (rubbing) alcohol. (Don't return to the woods or yard the same
day. Alcohol removes your skin's protection along with the urushiol and
any new contact will cause the urushiol to penetrate twice as fast.)
|Second, wash skin with water. (Water temperature does not matter; if
you're outside, it's likely only cold water will be available.)
|Third, take a regular shower with soap and warm water. Do not use soap
before this point because "soap will tend to pick up some of the urushiol
from the surface of the skin and move it around," says Epstein.
|Clothes, shoes, tools, and anything else that may have been in contact
with the urushiol should be wiped off with alcohol and water. Be sure to
wear gloves or otherwise cover your hands while doing this and then
discard the hand covering.|
Dealing with the Rash
If you don't cleanse quickly enough, or your skin is so sensitive that
cleansing didn't help, redness and swelling will appear in about 12 to 48
hours. Blisters and itching will follow. For those rare people who react
after their very first exposure, the rash appears after seven to 10 days.
Because they don't contain urushiol, the oozing blisters are not
contagious nor can the fluid cause further spread on the affected person's
body. Nevertheless, Epstein advises against scratching the blisters because
fingernails may carry germs that could cause an infection.
The rash will only occur where urushiol has touched the skin; it doesn't
spread throughout the body. However, the rash may seem to spread if it
appears over time instead of all at once. This is either because the
urushiol is absorbed at different rates in different parts of the body or
because of repeated exposure to contaminated objects or urushiol trapped
under the fingernails.
The rash, blisters and itch normally disappear in 14 to 20 days without
any treatment. But few can handle the itch without some relief. For mild
cases, wet compresses or soaking in cool water may be effective. Oral
antihistamines can also relieve itching.
FDA also considers over-the-counter topical corticosteroids (commonly
called hydrocortisones under brand names such as Cortaid and Lanacort) safe
and effective for temporary relief of itching associated with poison ivy.
For severe cases, prescription topical corticosteroid drugs can halt the
reaction, but only if treatment begins within a few hours of exposure.
"After the blisters form, the [topical] steroid isn't going to do much,"
says Epstein. The American Academy of Dermatology recommends that people who
have had severe reactions in the past should contact a dermatologist as soon
as possible after a new exposure.
Severe reactions can be treated with prescription oral corticosteroids.
Phillip M. Williford, M.D., assistant professor of dermatology, Wake Forest
University, prescribes oral corticosteroids if the rash is on the face,
genitals, or covers more than 30 percent of the body. The drug must be taken
for at least 14 days, and preferably over a three-week period, says FDA's Ko.
Shorter courses of treatment, he warns, will cause a rebound with an even
more severe rash.
There are a number of OTC products to help dry up the oozing blisters,
|aluminum acetate (Burrows solution)
|baking soda |
|Aveeno (oatmeal bath) |
|aluminum hydroxide gel |
|zinc acetate |
|zinc carbonate |
Desensitization, vaccines, and barrier creams have been studied over the
last several decades for their potential to protect against poison ivy
reactions, but none have been approved by FDA for this purpose.
Right now, prevention seems the best treatment, unless you plan to take
lessons from Batman's bane with Poison Ivy's name.
Isadora B. Stehlin is a member of FDA's public affairs staff.