Poison ivy (toxicodendron radicans) is the most common of the urushiol producing plants in the eastern U.S. Contact with urushiol oil is the substance that causes an allergic rash in 90% of the population.
Even a tiny amount (1 nanogram, a billionth of a gram) of sticky, resin-like urushiol oil will case a skin reaction. 1/4 ounce of the potent oil would be enough to cause a rash on the entire population of the earth!
Poison Ivy Facts:
- One must come into direct contact with urushiol oil to get the rash.
- Urushiol oil can be spread in smoke from burning plants and debris from lawnmowers or trimmers.
- Urushiol oil is still present in dead plants or vines and remains active for five or more years.
- Scratching the rash will not spread the rash (unless the oil is still on the skin)
- Fluid from the blisters will not spread the rash.
- Sensitvity to urushiol oil can develop at any time.
- Depending on individual reactions to urushiol oil can appear in hours or days.
The only sure way to avoid poison ivy rash is avoiding contact with urushiol oil directly from the plant or indirectly from clothing, tools, or gear that comes into contact with the oil.
Within fifteen minutes of exposure ururshiol oil bonds with the skin and a rash is likely. A long rinsing wash with cold water is an effective way to remove the oil. Warm water opens the pores allowing more oil to bond with the skin and soap may spread the oil more effectively.
If a rash develops there are many home remedies and commercial cures that provide some measure of relief. Check out the information available at the Poison Ivy, Oak and Sumac Information Center.
Toxicodendron Radicans profile from the U.S.D.A.