Log Cabin Chronicles

Royal Orr

Not all ivy climbs the hallowed walls

ROYAL ORR

It was a perfect day for a long stroll through the woods. Clear and very hot, but the sunshine was dappled and pleasant under the maples. We sat for a while with our toes in the stream, then headed home.

That night, as I pulled off my T-shirt to take a shower, I noticed some red welts on a patch of skin just above my belt line.

Forty-three years living in the country and here was my first bout of poison ivy.

It was a classic case. The red swellings, the little weeping blisters, the crusted lesions and, of course, the ITCHING! It was pretty well gone in a week's time. But I'm the kind of person who likes to know why I've just spent several days in mild agony, so for all you poison ivy sufferers out there, here's a primer on what the scientists call plant-induced allergic contact dermatitis.

Poison ivy, along with its near cousins poison sumac and poison oak, belong to a plant family that goes by the ominous Latin name of Toxicodendron.

When the leaves or stems of these plants are bruised or damaged by insects, the sap that escapes contains a compound called urushiol, an incredibly powerful allergen.

Some people are so sensitive to urushiol that it takes as little as two micrograms (less than one millionth of an ounce) on the skin to cause an allergic reaction. One expert estimated that the amount of urushiol needed to cover a pin-head is sufficient to cause rashes in 500 people.

If the sap is removed within an hour or two, most people have no reaction. But that's a lot easier said than done, and most of us don't even realize we've brushed up against a member of the Toxicodendron family (or worse, breathed it in as the plant burns - a particularly nasty problem that forest-fire fighters live with).

Urushiol rapidly penetrates the skin and binds with proteins in deeper epidermal cells forming a new compound called quinone. The quinone, attached as it is to protein molecules in your skin, acts as a red flag to your immune system.

Now that the stuff is in you, it's your T-cells that lead the charge. Somewhere in your past you had a brush with urushiol, even if it didn't turn into a rash. Your immune system created T-cells that recognize the urushiol-quinone invader and they've been patrolling your bloodstream and lymphatic system ever since.

After your stroll through the woods, the urushiol soaked through your skin and BANG! those T-cells were ready. They recognize the quinone-infected protein cells and call in an army of white blood cells.

White blood cells have a scorched-earth approach to fighting an invader. They basically kill everything in the area of the recognized problem - in this case quinone bound to skin cells.

Cells die and fluids from the dying cells are released producing a blistering rash. More fluid oozes from blood vessels and lymph systems and cell death causes breakdown of skin tissue. This process continues until all the quinone-affected skin cells are gone. This can take a couple of days, but in severe cases may take several weeks.

Eventually, the itching eases. The lesions heal. And that particular patch of skin remains especially sensitive to poison ivy for several years.

Experts say that you can go a long time without experiencing a reaction to poison ivy because thicker skin, like that on your hands, is an effective barrier to the urushiol. The danger is always that you'll transfer the compound to more sensitive skin.

So while I scratched, rubbed and soaked my way through my own mild bout, I took grim comfort knowing I'd escaped one of the common paths of poison ivy allergic reaction. Clinicians report that many men inadvertently transfer urushiol from their hands to their genitalia.

Makes you want to hold off peeing in the woods, doesn't it?

Royal Orr is a writer and broadcaster living in Hatley, Quebec.


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