Help! How long after being exposed to poison ivy would you start getting a rash?

2 to 10 days. The speed of a poison ivy rash depends on the thickness of the application of the oil responsible for the contact dermatitis (urushiol). Heavy applications erupt within 2 days; lighter hits take up to 10 days. If you think you have had contact, wash with soap and water asap and you may never get a rash. You can also get poison ivy up to a year after plant contact with tools, clothing, etc.