Can a poison ivy rash come out more with sun exposure?

I don't know about sun exposure, but I do know how poison ivy works, which may help. When an allergic person comes in contact with the powders or oils of the plant, he/she begins to have a reaction. As long as the oil or powder remains on the skin, the rash can spread and worsen.

Upon exposure or possible exposure to the plant, the allergic person should shower with soap and hot water to be sure all oils/powders are gone. Then, the healing process can begin, which takes about 7-10 days.

If the affected person has showered thoroughly, I would imagine the already sensitive rash is not responding well to heat or sunburn, hense the worsening of symptoms. Get out of the sun!