Once it touches the skin, the urushiol begins to penetrate in a matter of minutes. Redness and swelling will be followed by blisters and severe itching. In a few days, the blisters become crusted and begin to scale. The rash will usually take about ten days to heal, sometimes leaving small spot, especially noticeable in dark skin. Tips and Myths Poison Ivy can take up to 2 weeks to manifest itself .
Initial exposure can go undetected for a long period of time.
Scratching poison ivy blisters will spread the rash. This is not true. The rash cannot be passed from person to person - only urushiol can be spread by contact. 10 to 50 million people are affected by poison ivy a year. Once allergic, always allergic.