I've seen the term "contact dermatitis" many times but haven't bothered to actually understand precisely what it means. As I've been playing touchy-feely with all kinds of new to me plants, I'm wondering what the symptoms of contact dermatitis are? My now waning symptoms were pain on the fingerpads, stopping at the first joint. One pad still has a little swelling but the pain is pretty much gone. (My neighbor thought I might have gotten into nettles, but no such luck - I've still yet to identify stinging nettles. )

Answer:

That sounds like an immediate allergic reaction - rue is one plant that often does that. What is more often meant by contact dermatitis is a slower-to-start, much-slower-to-go-away inflammatory response - e.g. the reaction I get to xerox toner starts within minutes as a vague feeling of heat and discomfort, which subsides, with the skin going blistered, red, cracked and bleeding a day or so later, this persisting for about three months unless I treat it with steroids. Most cases of contact dermatitis are more like that; it's probably the commonest single health problem resulting from industrial or domestic work, though most people affected never report it. Can be caused by almost any substance people work with: metal or stone dust, detergents, bleaches, lanolin in wool, photographic chemicals, paint, solvents, oil, rubber, timber and sawdust, dyes...

Those quick-onset, quick-to-go allergic reactions can develop into true dermatitis on repeated exposure. Indian workers who handle cashews or mangoes (related to poison ivy - see the plant relationships file on my website) are very likely to suffer that way.

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