Skin rash... from weed killer??

I found a bumpy rash all over my legs on Monday and thought I might be getting poison ivy. But it hasn't gotten any worse. IT's still here on Wednesday and in thinking back about what could have caused it, I wore shorts on Saturday while spraying RoundUp on several areas of my yard. Could that have caused it? Do I need some kind of medication? Should it go away quickly?|||If you have washed off all the chemical, then time should head the rash.