Since summer finally decided to show up in Northern California, so have the poison oak rashes in my office. They range from a little localized mild redness to complete limbs covered in quarter-sized blisters. Nearly everyone is suffering from an intense itching and burning.
“But Doctor, I have never been allergic to poison oak before?” is a common statement from bewildered patients. Well there is a first time for everything. There is no immunity to plant allergens. Every time you expose your skin to the plant, you inch a little closer to becoming allergic. For some it can be in childhood and for others in their senior years; but at some point enough exposure will tip the scales against you. There are probably some truly blessed people that really are immune but I don’t how they would ever know. The threshold is different for each of us.
I like to joke with patients: “I appreciate that your rash is driving you crazy, but at least it is a good sign your immune system still works” Sometimes this elicits a laugh. In truth, a remarkable amount of cells in your immune system must work in chorus to produce that itchy red blister. If your immune system is severely depleted from HIV you may not even react to poison oak—but that is not a prevention method I recommend.
People mistakenly believe it is the resin from the plant causing their misfortune. But the plant resins are not caustic themselves in the sense acids or strong alkalis are. It is actually your own immune system that overreacts to the resin. That is why fluid from the blisters does not induce further rashes. By the time you get a blister, the resin is already dissolved deep into the skin. The fluid in the blisters is simply composed of immune system byproduct. Because your skin varies in its thickness from point to point, blisters that develop later on will create the illusion of spreading. Seeing is not believing in this case.
Some evidence does exist that the resin can trigger a body-wide reaction. This is why people will often notice a rash in an area that could not have possibly been exposed to the plant. Of course people touch themselves unconsciously in so many areas throughout the day so it’s difficult to say for certain. But once the resin binds to your skin, you cannot spread it to other people (but your clothes can).
Poison oak is a tremendous cause of worker compensation claims in fire fighters, telephone line workers, and landscapers due to direct exposure and also contaminated equipment. And a dead plant is not any less dangerous than a living one. The resins remain on the stalks and woody parts of the plant long after it has died. The burning of brush can even aerosolize it. Our good Cal Fire folks tell grizzly tales of this. Animals, especially hunting dogs and horses, are notorious for passing it along to the loving hands of their owners. The animals are spared the rash because the resin sits atop their fur and does not elicit any immune response.
The chemical urushiol is poison oak’s resin and responsible for all this misery. Spelling urushiol is worth eleven points in Scrabble. Getting urushiol often costs you a trip to the doctor. It is insoluble in water and takes about 15 minutes to bind to the skin. A landscaper friend of mine pulls an Indian Soap Root plant out of the earth and wipes it vigorously on the area, swearing it washes it off immediately—I’ve never tried it. Urushiol can last for years on your boots, gloves, and work tools. Wipe down tools with a disposable rag, hot water and dish soap. Hand soap doesn’t work well as anyone who has tried to wipe pine pitch off their hands knows. I also recommend a second wipe down with rubbing alcohol or a petroleum based product. For clothing, regular detergents are fine but wash at the highest recommended water temperature. Don’t overload your machine and it’s good to let the clothes agitate freely. The urushiol will then be suspended in the water and not transferred to other clothes in the load. If someone else does your laundry, give them a head’s up they are about to handle nasty stuff.
Poison oak is a remarkably resilient plant and can live in harsh environments. It will grow in full sun or partial shade, as a creeping vine, a bush, or ground cover. Watch out especially around fence lines and telephone poles. Everyone knows it famously has three leaves on a single stalk and that is the quickest method of recognizing it. Its leaves are typically bronze as they open, green in the spring, chartreuse or red in the summer and brilliant red or pink in the fall. Frankly, at a distance, I find it a dazzling plant to behold. Poison oak’s white flowers bloom in the spring and grow into greenish-white or tan berries. Birds consume the berries and bees buzz about the blooms unharmed.
Being a deciduous plant, the stems are leafless and bear only the occasional cluster of berries in winter. A leafless poison oak stem may sometimes be identified by black marks where its milky sap may have oozed out and caked on. Boy Scouts are taught to carefully wipe a piece of paper across a broken plant and watch for the ensuing black streak to confirm it is poison oak. Don’t feel stupid if you mistakenly come in contact with this chameleon though. I’ve misidentified it myself as it often mimics the size and shape of the plants it is growing amongst. Scientists tell us we can look forward to only more poison oak if predictions of rising CO2 levels hold true; in labs the plant reportedly thrives with higher CO2 concentrations.
The treatment of poison oak consists of putting the brakes on the immune cascade once the resin has been bound to your skin cells. Typically topical cortisones and oral antihistamines alleviate the majority of cases. Calamine, menthol, cold packs, and oatmeal baths are just a few of the many soothing treatments that help make life more bearable. Several other topical preparations like pramoxine and diphenhydramine (benadryl) are good. When people are miserable and can’t get to me, I sometimes recommend an OTC benzocaine preparation to just completely numb the area. It is the same stuff you would buy to soothe bad sunburns and usually mixed with some aloe. My favorite treatment is Sasquatch Itch Cream™ if the rash has already erupted. Even if you are not in an austere location, it is worth applying because it may save you a trip to the ER. Sometimes however, the rash of poison oak is too advanced and one needs a good old-fashioned injection of cortisone from their doctor.
Occasionally the allergic cascade will brew into a serious allergic tsunami that causes asthma symptoms and low blood pressure necessitating a trip to the local ER. Lesions also can become secondarily infected. Biotech companies have been working on a vaccine for sensitive individuals for the last twenty years. Of course if you can wash urushiol off in the first 10-15 minutes that is the best treatment. Technu is such a product (Of interest, Technu was first formulated to wash off radioactive dust particles at nuclear test sites). But remember, once the resin has set in, you are dealing with your hyperactive immune system rather than the resin.
In the early days of anthropology it was reported that Native Americans were less sensitive to urushiol. It is now believed that the children had a greater awareness and were more “in tune” with avoiding it. There is probably a great gap in our understanding of how Native Californians interacted with this plant. Supposedly, they were able to wrap cooked food in the leaves and weave baskets with the stalk and apparently not suffer. They did recognize its blister-inducing properties could treat warts, and was also used for rattlesnake bites in some fashion. The only real racial factor known is that Asians may be slightly less likely to get a rash due to early exposure in life to mangos and Japanese lacquer, which chemically resembles urushiol. Botanists usually agree poison oak and poison ivy are New World plants, as Capt. John Smith is credited with the first formal description of the plant by a non-native person.
Poison oak has been and will be here long after us. Like rattlesnakes and mosquitoes, you’ll eventually run into it if you spend time outdoors here. Educate yourself and family on it but don’t forget to live life and enjoy this wondrous outdoor paradise we call home.
Further reading recommendations: