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Poison Ivy
Poison Ivy, Oak & Sumac
What causes the rash?
Poison ivy, oak, and sumac are plants which cause an itchy skin rash when directly contacted. The rash is a true allergic response to an oil called urushiol found in the sap of these plants. This oil is a sticky, clear to slightly yellow, and odorless substance which turns dark on exposure to air. Urushiol oils from different plants vary slightly chemically from each other and occasionally individuals can be allergic to one and not the other. The urushiol oil is expelled by an injured plant and can be carried on the surface of objects, clothing, or animals that have come in contact with the toxic sap. These plants can also produce a toxic vapor when burned which can injure the lungs and windpipe (trachea) if inhaled.
Plant Identification
Poison ivy, oak and sumac plants producing urushiol belong to the biological family known as the anacardiaceae family. Most belong to the genus Toxicodendron (T) and several species are know in the United States. For example: T. diversilobumo and toxicarium (poison oak), T. vernix (the poison sumac) and T. radicans (poison ivy). Although these plants like to grow in moist, warm places, their geographic distribution is fairly widespread. They are unknown in Hawaii and northern Alaska. In general, poison oak grows west of the Rockies and poison ivy to the east. Poison ivy and poison oak typically have three leaves per stem, but may have more than three leaves. (So the old adage "leaves three, leave be" is not always correct!) Poison sumac has a longer stem with 7-13 leaves. These plants appear different depending on their location and the season. The toxic sap content is most abundant in spring and summer.
Who is susceptible?
80% of the population will develop a skin rash when contacting the leaves of the poison ivy plant. The severity of the rash varies from person to person. People between 5 and 20 are the most vulnerable to severe forms of skin reaction. Older persons generally have less severe disease. 10% of people develop very severe skin reactions with major swelling and itching.
What does the rash look like?
The ivy oil urushiol penetrates the skin within minutes. First, redness and swelling at the site of contact are visible. Gradually, itching becomes more intense. Blistering of the skin appears within 24- 72 hours (sooner if this is not the first reaction). The typical rash is arranged as a red line on an exposed area of the body caused by the plant dragging across the skin. However, patches of skin rash can break out on the neck or between the fingers. The rash will continue for up to two weeks. If the skin is broken by scratching, infection of the skin can complicate the condition.
What is the treatment for poisoning from these plants?
The best treatment for this malady is prevention, as unfortunately no cure is currently available. Usually, the rash will clear by 14 days and treatment is directed at controlling the itching. Antihistamines (like Atarax or Benadryl) taken orally can be very beneficial. For mild cases, topical cortisone can be soothing as can cool compresses of Burrow's solution.
Cortisone medications are given by mouth if the rash is severe. Generally, these are given early on and only if there is extensive exposure or severe skin sensitivity. If the skin becomes infected, antibiotics may be necessary. The blister fluid does not contain any of the toxic agent and will not spread the rash.
How can poisoning from these plants be prevented?
The only true way to prevent this miserable problem is to avoid contact with the toxic oil of the plants. Long pants and sleeves are very important if you are venturing into an unknown wilderness area. If possible, wear gloves, boots and a hat.
Learn to recognize these plants and avoid them.
A new barrier cream called Ivy Block or bentoquantam 5% can be applied to the skin prior to exposure and will form a protective layer on top of the skin. The drug Trental may decrease the rash slightly, but needs to be taken before exposure to the plants. Immunization for poison ivy, oak or sumac is not available at this time.
Avoidance is the key.
What can be done if exposed? - Wash all exposed areas of the skin with cool water. Flowing water is better to irrigate and remove the urushiol oil. Use a nearby stream, river or garden hose if available. If soap is used, wash it off the body and do not spread to other areas.
- Wash all clothing as this may have been contaminated by urushiol oil.
- Wash all possible contaminated gear as well as animals.
- Contact your healthcare practitioner.
- Most people are susceptible to the rashes of poison ivy, oak and sumac.
- The sap oil, called urushiol, causes the skin rash.
- Poison ivy is not contagious.
- Wash the oily sap from the skin with water and soap immediately.
- Avoiding direct contact with the plants can prevent the rash.
Last updated on 05/15/2008
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