Sixth Grade
Worksheets
How Does Poison Ivy Work?
"Leaves of three, let it be." That old advice is all some people need to hear about poison ivy. Other people, however, want to know the whole story. They want to know how poison ivy causes itching. What is it about this common three-leaved green plant that makes more people allergic to it than to any other substance?
That's right - poison ivy rash is an allergy, the most common one in the United States. Up to three-fourths of the people in the country are allergic to this plant, and millions of people break out with this itchy, red rash every year.
The poison ivy rash that makes so many people miserable is a reaction to a substance in poison ivy plants called urushiol. Urushiol is very powerful. The tiniest drop, one-billionth of a gram, is all it takes to cause an allergic reaction. People come into contact with it when they are working in their yards or taking a hike.
