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Poison Ivy

shutterstock_66518167Poison Ivy

An oleoresin (urushiol oil) in the plant sap of the Poison Ivy plant (Rhus radicans) is the allergen that can cause a skin reaction in up to 80% of people.  The first time a person reacts, the rash will begin 1 to 4 days after skin contact. The reaction will appear as a red, swollen area followed by small blisters that are intensely itchy.  The rash can last 2-3 weeks.  On subsequent exposures, the rash starts earlier and usually resolves after 7 to 10 days. The oleoresin can unknowingly be transferred to other seemingly protected areas (privates) if it is on the hands.  The rash is frequently in linear patterns (lines) from brushing of stems against the skin.  The oleoresin oil can become airborne when the plants are burned and contact with smoke or inhalation can induce symptoms.

Similar substances to the oleoresin are found in other plants in the same family including poison oak, pistachio, poison sumac, mango, cashew, Brazilian pepper and poisonwood (Metopium toxiferum).

Allergic contact dermatitis:  this is a type IV allergic reaction mediated by T lymphocytes of the immune system and is permanent.  It is not mediated by IgE, so there is no skin or blood test to confirm allergy and desensitization is not effective or practical.  Allergic contact dermatitis is rare in children less than 10 years old.

What to do if you have poison ivy contact:

  • Washing the area immediately (15 minutes) with soap and water after contact will prevent pain and suffering.  After 15 minutes, the antigen becomes “fixed” to the skin and cannot be removed!
  • Small areas can be treated with soaks, baths, or compresses 3 times a day for 10 to 20 minutes.
  • Follow soaks with potent topical corticosteroid cream (over the counter cortisone may not be potent enough). Your physician can recommend the appropriate cream or ointment based on the location and severity of the rash.
  • Oral antihistamines can be used to decrease itching and diphenhydramine (Benadryl) may aid in sleep if taken at bedtime
  • Wash the clothes or other items thoroughly to remove the resin.
  • If a pet was along on the hike, wash the pet as there can be transfer from the pet fur.
  • If the rash is severe or widespread, oral steroids such as prednisone may be prescribed by your doctor.

How to prevent poison ivy contact:

  • Identify the plants.  Poison Ivy is a vine that can grow as a single plant, a climbing vine or a shrub. Poison ivy can be found nearly everywhere including woods, fields, vacant lots and even your own back yard. The plants tend to grow along fences and stone walls. They prefer sunny areas along the edges of forests and fields.  Look at the leaves and remember “leaves of 3, let them be!”  The cluster of 3 leaves on a long stem can be bright or dark green and appear waxy.  They turn red in the fall.  Even in fall and winter, the oil can be present on stems so must be avoided.
  • Barrier creams: Ivy Block and Stokogard can reduce skin outbreaks by as much as 70% if applied to exposed areas BEFORE contact.  It’s still important to wash clothing that came into contact with the plant.

Summer is just around the corner and that means hiking and outdoor activities that increase your risk of poison ivy exposure.

This educational information does not take the place of your physician’s advice.

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