Danny D. said:


On Mon, 01 Jul 2013 07:47:19 -0400, Pat Kiewicz wrote:

http://www1.picturepush.com/photo/a/...g/11947484.jpg
it's still automatic for me to ID poison ivy, oak, or sumac
I am amazingly good at spotting it.

I understand what you mean, as I am always identifying it for the
grandkids, who wander by oblivious to all harm.

Nobody is immune to cell-mediated immune responses (since the T-Cell
are randomly generated and passed by the Thymus), but some people just
haven't (randomly) gotten it yet. Or, they haven't gotten enough of a
dose that their T-Cells wandered by a urushiol quinone which has
bound to a receptor site on a Langerhans cell in their skin.

NOTE: Contact dermatitis is NOT mediated by humoral antigen/antibody
responses, so, all the conventional wisdom of "being immune" goes out
the door.

I've never gotten a rash from poison ivy, even when (as a kid) I was dared
to rub a leaf on my skin, or when I've pulled seedlings out bare-handed.
My dad's side of the family, very vigorous reactors. My mother never has,
if I recall correctly.

Which is sort of odd, as both my mother and I have had serious
reactions to other chemicals and adhesives. I've had at least one
quite serious case of photoallergic dermatitis which required
(unpleasant) steroid therapy and I have to carefully read labels to
avoid certain preservatives and also avoid sun-screens other than
zinc oxide. I mainly rely on sun protective clothing and hats,
which means long sleeves and long pants no matter how hot it is.
(Coolibar makes some clever items, but it's still easy to overheat.)

In the case of the amount of sap in that picture, almost nobody on
earth would not respond to that amount, were it to touch skin (keeping
in mind, the urushiol oil is known to stay active over 100 years in
dendrology drawers) and probably 10 years in my relatively dry climate.

That I could believe.
--
Pat in Plymouth MI

"Yes, swooping is bad."

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