An id and an itch

WHAT IS IT about sex and poison ivy, anyway? First there's that great Coasters song from 1959 ("Late at night while you're sleepin' poison ivy comes a'creepin'/ Arou-ou-ou-ou-ound") and now comes the revelation that if you get poison ivy often enough your body can become susceptible to rashes even in places where you haven't been exposed, and this is called an "id reaction." Really - what would Sigmund Freud say about that?

How can one plant be so - so hurtful? One youthful frolic in the underbrush and you just can't get it out of your system, ever. You can spend years cultivating a nice sedate Virginia creeper, and living the good life, and then just a single passing moment with that old flame, Toxicodendron radicans, and you've got that familiar itch all over again.


And here's where it gets really heartbreaking - it's your own reaction, rather than the direct effect of the poison ivy oils, that makes you so miserable. OK, it may not be sex, but it sure sounds a lot like love, doesn't it?

Poison ivy and its cousin, poison oak, grow throughout North and South America and in eastern Asia. The sap contains an oil called urushiol, and what happens, says Dr. Phillip M. Williford of the Wake Forest University Medical Center, is that the urushiol permeates the outer layer of your skin - it doesn't get under your skin, it gets into your skin - and "binds irreversibly" with the cells there. Your body, if it has been exposed to urushiol at least once before, recognizes it as "foreign and bad," and mounts an immune response to get rid of it. Unfortunately, the immune response leads to an incredibly itchy rash that ends in blisters, but you don't shed the urushiol until the skin cells it has attached to naturally fall off. This takes about two weeks - of pure agony.


As anyone who has ever stood looking at a back yard must know, poison ivy is nefarious, insidious and duplicitous. It grows like a vine or a shrub. It likes moist soil, but it also likes dry soil. It revels in sunlight, and prospers in shade.

This summer it has been spreading out there like nobody's business. It's easy to avoid the ostentatious banks of it ("leaflets three, leave it be"). What gets you is that little sneaky shoot under the hedge, or behind the forsythia, or twining through the fallen leaves at the edge of the woods.

You get it on your hands and don't even realize it, and spread it around and then it's on your clothes - where the urushiol crystallizes and becomes about as permanent as the pyramids - and a day or two later the torture begins in earnest. "The urushiol is a very sneaky son of a gun," says Dr. William L. Epstein of the Skin Disease Research Foundation in San Francisco. It just keeps giving and giving of itself. A man in Texas once got urushiol on the steering wheel of his car, picked it up on his palms (which are generally not susceptible to it) every time he drove, and gave his manicurist a weekly dose of poison ivy - for several months running.

For most people, every time you get it it's more intense than the time before. Your body cranks up a bigger and bigger response. For an unlucky few, eventually, the "id" kicks in, and you can burst out anywhere in a sympathetic rash - and technically this isn't the psychoanalytic id we're talking about, but sort of an immune system version of it. Anyway, it's out of control.

Why? Why would a plant be so cruel?

It's not about you, says Susan Pell, a lab manager at the New York Botanical Garden. The urushiol isn't there to punish you or your libido, but to kill off insects that want to eat the poison ivy. "And we just happen," says Dr. Epstein, "to be in the way."