Photosensitization : causes?

[Jeff Wagner]

> And, of course, Rhus.  The ornamental varieties are bad - I got a burn
> on my arm once, as bad as if I had touched it against my motorbike
> exhaust, when I brushed against one while cutting grass with a motor
> scythe, but the North American Poison Ivy (also a Rhus) is diabolical.
> 
> Roger Riordan.

In the Arboretum at Horsholm, N of Copenhagen, they have a beautiful
clump of poison ivy.  So many people walked up to it to examine it that
they finally gave up and put a cage around it.