A poison ivy rash generally appears within 12 to 48 hours after exposure to the plant's urushiol oil. However, the timing can vary depending on factors such as whether it's the first exposure or a subsequent one, the amount of exposure, and the sensitivity of the person's skin. For someone with previous exposure, the rash usually develops faster (within 4 to 48 hours), while for a first-time exposure, it can take 2 to 3 weeks for the rash to show up. The rash typically lasts between one and three weeks depending on severity and individual response.
