It’s a pretty spring day and you can’t resist the urge to do a little spring-cleaning in the yard and flowerbeds. You pull out weeds, trim a few bushes, and maybe even burn some dead branches. Later that evening you absent-mindedly scratch a small but persistent itch. Within hours you realize that the irritation has spread and you have a full-blown rash caused by exposure to poison ivy. You are not alone; nearly 90% of the population is allergic to urushiol, the oil found in poison ivy, oak and.