Phytophotodermatitis

I love learning new stuff. And, of course, personal experience is the best teacher. But I'd rather have learned this new word at second or third hand.
You may (or may not) remember my post about the severe rash I had after pruning the abundant rue in my herb garden last Friday. I thought it was like poison ivy rash -- it itched and made little blisters -- but it didn't respond to the hydrocortisone cream in the way that poison ivy does and, along about Tuesday, with my hands looking like something out of a horror movie, I made an appointment with our local clinic. 
My appointment was for the afternoon so I decided to ask Mr. Google about rue allergy in order to tell the doctor what I thought was going on. And by the time I'd checked out various sites, I realized that this pestilence was just going to have to run its course (5 to 7 days or longer) -- there is no magic bullet. So I cancelled my appointment and went to the store and bought four different over the counter creams and sprays (Gold Bond ointment is my favorite.)
 But I digress. What I wanted to tell you was about this cool new word with which I am now intimately familiar --  Phytophotdermatitis.  Phyto (plant) photo (light)  derma (skin)  -itis (inflammation.)  Or something like that.

What it means is that there are a number of plants -- rue being one -- that secrete oils which, if rubbed on one's skin and then exposed to sunlight,  will cause skin irritation, far more akin to severe sunburn than to poison ivy rash. The rash may take on a darker or lighter appearance which may take weeks or months to fade. One could presumably roll naked in the rue by moonlight and suffer no ill effects -- as long as one bathed well before the sun rise. I know I've read in old herbals and folk medicine books about plants that should be harvested by moonlight or in the dark of the moon. Now I think I know why. 

 In my reading  I also learned of a case in which a parent was suspected of child abuse because of a lingering handprint on their child. Turned out the parent had been handling one of the plants that causes this reaction and then had laid their hand on the child's skin. And then the child had gone out in the sun...
Oh, I see lots of potential for working this little known plant/sunlight reaction into a story!
It's not just rue either. Plants causing this reaction include meadow grass, carrots, wild carrots (Queen Anne's Lace,) parsnip, celery, limes, lemons, fig leaves, mustard, and chrysanthemums...
As for me, the itching has subsided somewhat and my hands are beginning to peel. A lesson learned...