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Clinician’s Corner: Poison Ivy

Poison Ivy—The basics                                                                  

The Toxicodendron (“means poisonous tree”) genus of plants causes more contact dermatitis than all other causes combined.  Ten to fifty million Americans develop allergic contact dermatitis to a Toxicodendron annually.  In one study 10% of all occupational injuries among seasonal farm, workers in PA and NY were due to poison ivy contact.  The Latin names are as follows:

  • common or northern poison ivy (Toxicodendron radicans)
  • western poison ivy (Toxicodendron rydbergii)
  • eastern poison oak (Toxicodendron toxicarium)
  • western poison oak (Toxicodendron diversilobum)
  • poison sumac (Toxicodendron vernix)

Regardless of the species name all the treatments are the same. Allergic Contact Dermatitis (ACD) has 2 distinct phases.

  • A sensitization phase where the skin becomes “sensitized” to the oil in the plant
  • An elicitation phase where the skin breaks out in a rash.

Identification of Poison Ivy:

  • Poison ivy is typically a hairy, ropelike vine with three shiny green (or red in the fall) leaves budding from one small stem. “Leaves of three let them be!” and “Hairy vine, no friend of mine”.
  • May have yellow or green flowers and white to green-yellow or amber berries
  • Poison sumac, may be harder to identify because it more often forms leaflets of five, seven, or more that angle upward toward the top of the stem. Poison sumac presents as a woody shrub that has stems that contain 7-13 leaves arranged in pairs

Here’s what happens

  • Urushiol, which is a varnish like substance that oozes from the broken leaf and stems, causing the characteristic black dots which is oxidized urushiol and can be found on plant leaves within 10 minutes of its exposure to oxygen. Urushiol can be transmitted to the patient by contact with the plant, or pets, tools, gloves, shoes and clothing for months.  Washing clothes in regular laundry detergent will decontaminate fabrics.  Poison Ivy should NEVER be burned, as it vaporizes the oil, causing lung damage.
  • The characteristic blisters of poison ivy contain serum, and NOT the urushiol. Poison ivy and other poison plant rashes can’t be spread from person to person. But it is possible to pick up the rash from plant oil that may have stuck to clothing, pets, garden tools, and other items that have come in contact with these plants.

When contacted:

When exposed to a poisonous plant, like poison ivy, oak or sumac:

  • Immediately rinse skin with rubbing alcohol, poison plant wash, or degreasing soap (such as dishwashing soap) or detergent, and lots of water. A bar of Fels Naphtha soap (old fashioned washboard soap) a in nylon stocking, can be carried by canoeists or backpackers. The soap is always handy, and never gets soggy.
  • Rinse frequently so that wash solutions do not dry on the skin and further spread the urushiol.
  • Scrub under nails with a brush.
  • Wash exposed clothing separately in hot water with detergent.
  • After use, clean tools with rubbing alcohol or soap and lots of water. Urushiol can remain active on the surface of objects for up to 5 years. Wear disposable gloves during this process.

Next week…treatment and prevention of poison ivy.