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Contact Dermatitis

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Poison Ivy

  • A perennial, high-climbing, woody vine.
  • Leaves are alternate, deciduous, pinnately compound; leaflets three, thin, bright shiny, ovate to elliptic, 1.5 to 4.75 inches long, 1.5 to 4.75 inches wide, entire serrate to shallowly lobed.
  • Flowers small, yellowish green, in clusters of axils.
  • Fruit a scarcely fleshy drupe, glabrous to short pubescent, 0.15 to 0.20 inches
  • Poison ivy can be found in every region of the United States, except the Southwest, Alaska, and Hawaii. It appears as a weed with three shiny green leaves and The plant typically grows in the form of a vine, often along riverbanks, in woods, but also in pastures, fencerows, and roadsides.

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Poison Oak

  • It grows in the form of a shrub 1 to 6.5 feet tall and has three leaves similar to poison ivy, however, it does not climb.
  • Leaflets are thicker, dull green, hairy on both surfaces, broadest above the middle, and often lobed or coarsely serrate.
  • Fruit is densely pubescent rather than glabrous or short pubescent.
  • Found on the West Coast and throughout the South most abundant on relatively dry, sunny sites in woodlands, thickets, and old fields.

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Poison Sumac

  • Poison sumac grows abundantly along the Mississippi River, but is less common in other regions.
  • It grows as a woody shrub. Each stem contains 7 to 13 leaves arranged in pairs.

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  • The Poison Ivy and Poison Oak toxin resin (oily sap) is found in its stems and leaves.
  • All parts of the plants are poisonous.
  • The toxic principle is a phenolic compound called urushiol. It is a skin and mucous membrane irritant and is found in all parts of the plant.
  • Some humans are quite sensitive to the effects of the toxin while others show no ill effects from coming into contact with the plant.
  • The toxin has little or no effect on animals, but pets may carry the irritating substance on their hair and thereby transmit it to humans.

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  • This is a form of contact dermatitis caused by an allergic reaction to the resins (oily sap) of the poison ivy, oak, or sumac plant.

  • The rash is spread only when the oils come into contact with different areas of skin. It is not spread by the fluid of the blisters it creates, thus it is not contagious unless the resin remains on the skin and is touched by another person.

  • The reaction and rash in susceptible humans usually starts with itchiness and swelling followed by the reddish inflammation of tiny pimples or formation of blisters at the areas of contact.

  • The rash can vary in severity from person to person and from year to year on an individual.

  • The rash can begin as early as an hour after contact or up to five days after contact.

  • The oily resin usually enters the skin rapidly, and is seldom-transferred person to person. Conversely, the resin may persist for long periods on contaminated clothing, pets, tools, etc., and sensitive individuals can easily develop the rash from delayed contact with contaminated items.

  • Severe cases can occur from exposure to smoke from burning Poison Ivy and Poison Oak.

  • Worst stage of the rash is experienced 4 to 7 days after exposure. Rash may last for 1 to 3 weeks.

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  • The skin should be washed thoroughly with soap and cool water as soon as possible following exposure. Because the resin enters skin quickly, it must be washed off completely within 30 minutes to prevent a reaction. Scrub under the fingernails with a brush to prevent spreading of the resin to other parts of the body by touching or scratching. (Use cool water to wash skin. Warm water opens pores and may allow urushiol to penetrate deeper into the skin causing a more severe reaction.)

  • Calamine lotion and topical hydrocortisone cream may be applied to the skin to help decrease itching and blistering.

  • Antihistamines, such as Benadryl (diphenhydramine) help relieve itching and can be mildly sedating. Bathing in tepid water with one cup of Aveeno oatmeal per tub may also soothe itchy skin. Aluminum acetate (Domeboro solution) soaks can also be helpful to dry the rash and reduce itch.

  • Some people have severe allergic reactions to these plants and can have swelling in the throat, breathing problems, weakness, dizziness and bluish lips. If any of these reactions occur, seek emergency medical care.

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Prevention and Control Methods

  • Learn to identify poison ivy, oak, and sumac to avoid exposure.

  • Cover skin with clothing (long sleeves, long pants, shoes, and socks) when walking in the woods or in areas where these plants may grow.

  • Use barrier cream such as Ivy Block or Stokoguard when working in areas where poison ivy is present.

  • Be aware of resins carried by pets.

  • Wash exposed skin thoroughly with soap and cool water as soon as possible following exposure.

  • Also, keep your hands away from your eyes, mouth and face.

  • Wash the clothing and shoes of the exposed person with soap and hot water. Resin can linger on these surfaces for days.

  • May and June are the best times to apply control measures to these poison plants, but it can be done any time of the year.

  • Burning can be dangerous and is not recommended for disposal or as a control measure because the toxic oil from the plant can be carried in smoke.

  • Spraying the foliage with glyphosate (sold under the trade names of Roundup or Kleenup and others) is recommended.

  • Remember that the vine left on the tree or fence still has oil in it so be careful if you pull the vine down. Even if the vine is brown and looks dead, it still may have oil in it.

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Contact Dermatitis