Some years ago, I got a rash from my ankles to my kneecaps. I had previously been cleaning out our farm pond and initially thought that was the culprit. When I finally sought help from a dermatologist, he diagnosed my rash as phyto-photo-dermatitis and thought it was more likely I had been in contact with a weed in the umbelliferae family. He told me it was the combination of sunshine activating the plant at a certain stage of its life causing it to release toxins that I was sensitive to. That rash lasted at least 2 months and was quite unsightly. I've never had a repeat experience, so it must have just been some random collision of all three factors.
