Poison Ivy

Poison Ivy Source: Encyclopedia Britannica "Either of two North American species of white-fruited woody vines or shrubs of the sumac, or cashew, family. The species found in eastern North America (Toxicodendron radicans) is abundant; a western species, known as poison oak, is less common. Both species are sometimes classified as genus Rhus. A key identifier is leaves with three mitten-shaped leaflets. Contact with urushiol, an oil produced by the plant, can cause severe inflammation and blistering of human skin. Urushiol may be carried from the plant on clothing, shoes, tools, or soil; by animals; or by smoke from burning plants. Because urushiol is nonvolatile, a reaction may result from wearing clothing a year or more after its contact with the plant."

Less common in Florida, but still occasionally encountered are Poison Oak, and Poison Sumac. They both contain the exact same substance, Urushiol Oil, so for the purposes of this article to make things less confusing we'll just use the term Poison Ivy. Poison Ivy The most common type in Florida Leaf forms among plants, or even on the same plant, are as variable as the habit of growth; however the leaves almost always consist of three leaflets. The old saying, "Leaflets three, let it be," is a reminder of this consistent leaf character. Flowers and fruit are always in clusters on slender stems that originate in the axils, or angles, between the leaves and woody twigs. Berrylike fruits usually have a white, waxy appearance.   Poison Oak Poison oak is more distinctive than some other types of ivy. Some people call it oakleaf ivy while others call it oakleaf poison ivy. Poison oak usually does not climb as a vine, but occurs as a low growing shrub. Stems generally grow upright. Leaflets occur in threes, as in other ivy, but are lobed, somewhat as the leaves of some kinds of oak. The middle leaflet usually is lobed alike on both margins and resembles a small oak leaf, while the two lateral leaflets are often irregularly lobed. The range in size of leaves varies considerably, even on the same plant.   Poison Sumac Leaves of poison sumac consist of 7 to 13 leaflets arranged in pairs with a single leaflet at the end of the midrib. The leaflets are elongated oval without marginal teeth or serration. They are 3 to 4 inches long, 1 to 2 inches wide, and have a smooth, velvety texture. In early spring their color is bright orange. Later, they become dark green and glossy on the upper surface, and pale green on the lower, and have scarlet midribs ( a very distinctive feature). In the early fall, leaves turn to a brilliant red-orange or russet shade.

Outsmarting Poison Ivy and Its Cousins

Source: U.S. Food and Drug Administration
William L. Epstein, M.D., Professor of Dermatology, UCSF
Hon-Sum Ko, M.D., Allergist and Immunologist, FDA

Approximately 85 percent of the population will develop an allergic reaction if exposed to poison ivy, oak or sumac, according to the American Academy of Dermatology.

Usually, people develop a sensitivity to poison ivy, oak or sumac only after several encounters with the plants, sometimes over many years. However, sensitivity may occur after only one exposure.

The cause of the rash, blisters, and infamous itch is urushiol (pronounced oo-roo-shee-ohl), a chemical in the sap of poison ivy, oak and sumac plants. Because urushiol is inside the plant, brushing against an intact plant will not cause a reaction. But undamaged plants are rare.

"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.)

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, including:

• aluminum acetate (Burrows solution)
• baking soda
• Aveeno (oatmeal bath)
• aluminum hydroxide gel
• calamine
• kaolin
• zinc acetate
• zinc carbonate
• zinc oxide

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.

Links to Additional References on
Poison Ivy and Urushiol Oil:

Harvard Medical School
Consumer Health Information - Poison Ivy Prevention and Treatment
www.intelihealth.com/IH/ihtIH?t=8214

John's Hopkins School of Medicine
Poison Ivy, Poison Oak, and Poison Sumac
www.jhu.edu/~shcenter/poisonivy.html

New York University Medical Center
Poison Ivy, Poison Oak, Poison Sumac (Allergic Contact Dermatitis)
www.med.nyu.edu/patientcare/library/article.html?ChunkIID=11616

Univerity of Illinois Medical Center
Poison Ivy, Poison Oak, and Poison Sumac dermatitis
uimc.discoveryhospital.com/main.php?id=132

University of Chicago Medical Center
Poison Ivy / Poison Oak
www.uchospitals.edu/online-library/content=P00306

Princeton University
Poison Ivy, Sumac and Oak
www.princeton.edu/uhs/ih_Q_A_skin_care.html#poisonivy

University of Notre Dame
Poison Ivy Allery - PDF Document
uhs.nd.edu/PDF/poison%20ivy_2004.pdf

Perdue University
Student Health Center - Poison Ivy
www.purdue.edu/push/pages/moreinfo/homepage/poisonivy.shtml

Poison Ivy, Oak & Sumac Information Center
Contains Facts and Myths about Poison Ivy:
poisonivy.aesir.com/view/fastfacts.html

U.S. Pharmacist Magazine
Poison Ivy/Oak/Sumac - What Your Patients Need to Know
www.uspharmacist.com/index.asp?show=article&page=8_1281.htm

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