Poison ivy and poison oak: these are dirty words for people who work and play outdoors. Along with their cousin, poison sumac, they’re responsible for painful rashes that can linger much longer than the enjoyment the sufferer might have experienced by being outdoors.
And when you’re suffering through a weeks-long rash that it seems nothing will affect, the most important thing in the world is a relief. This article explains the cause of painful dermatitis acquired from contact with these toxic plants and outlines the best ways to treat it.
The Poisonous Tree
All three of the common “poison” plants — ivy, oak, and sumac — belong to the genus Toxicodendron (“poisonous tree), a genus endemic to most of North America. Each species varies widely from place to place, but fortunately poison oak and ivy are usually distinguishable by the presence of white berries and three triangular, often (but not always) serrated leaves per leaf-cluster.
Poison sumac bears 7-13 leaves per branch and produces white or green berries. Poison sumac can grow into a tree; poison ivy and oak may appear as bushes, vines, creepers, or individual plants. Like all members of the Cashew family — including pistachios, cashews, the Japanese lacquer tree, ginkgoes, and the Brazilian pepper tree — Toxicodendron species secrete a resinous oil, the active ingredient of which is called “urushiol.”
Urushiol isn’t a true poison; it is, instead, an allergen that seems specifically targeted at humans — virtually no other species are susceptible to it. Some, like goats, can even eat Toxicodendron plants, a practice that would be exquisitely painful for most humans. Like all allergens, urushiol causes problems by stimulating the human immune system to attack its own tissues; indeed, urushiol has been called “the fiercest allergen known.” Just a few drops can cause rashes in hundreds of people.
For most, contact with the oil or with oil-laden smoke results in painful swelling and/or a hive-like rash. For the occasional individual, urushiol can cause kidney failure and even death; fortunately, this sort of extreme reaction is very rare.
Urushiol is not only virulent, it’s extremely resilient and long-lasting — people have gotten rashes from handling Toxicodendron herbarium samples that are hundreds of years old. Fortunately for the species, perhaps 25% of the population is blissfully immune to the effects of urushiol. The rest of us react to it to one extent or another. In most cases, the resultant rash lasts 1-3 weeks.
As with many such things, an ounce of prevention is worth a pound of cure; it’s best to simply avoid Toxicodendron plants altogether. Sometimes, however, this is impossible — poison oak, ivy, and sumac are surprisingly widespread, appearing everywhere from deep woods to backyard gardens. There’s no real cure for the rash, but the following section outlines the best treatments for Toxicodendron dermatitis.
The list of putative treatments for Toxicodendron dermatitis is as extensive as human imagination, and not a single one actually cures the underlying problem — that is, the allergic reaction to urushiol. Everything has been tried, from herbs to horse urine to gunpowder.
While some of the remedies ease the pain and itching of dermatitis, the only thing that actually cures it is time. That said, there are some things you can do to either avoid the itch or treat its symptoms. These methods fall into two broad categories: palliatives and preventatives.
Palliative remedies seek to treat the symptoms of Toxicodendron dermatitis, rather than actually effecting a cure. Recent studies indicate that the best low-tech treatment is good old calamine lotion, that pinkish zinc-oxide mixture that just about everyone knows to use.
It doesn’t cure the rash, but it certainly cools and soothes the skin, if only temporarily. Oatmeal baths can also bring temporary relief. Interestingly, hot water can help soothe the pain for a short time.
Anti-itch medications would seem to be in order, but in most cases, they don’t work well. Antihistamines are mostly useless, because few histamines are released at the rash site, and anything containing phenol or camphor can cause severe skin irritation.
Benzocaine and related medicines may cause allergic reactions. Hydrocortisone, a commonly prescribed palliative, is useless in concentrations of less than 2%, and in higher concentrations can be dangerous to one’s system.
Similarly, prescription corticosteroids — either in pill or injection form — can throw your bodily functions seriously out of whack. They work very well for the itching but can cause adrenal problems, increase blood pressure, cause swelling of the face and neck, and disrupt the female menstrual cycle for months. Of course, individuals with extremely bad cases of dermatitis may be willing to change these effects in the quest for relief.
The ultimate preventative measure against Toxicodendron dermatitis is to avoid Toxicodendron species altogether; however, the reality of this approach has already been discussed. Studies suggest that urushiol molecules take between three minutes and an hour to bind with the skin, so it’s theoretically possible to remove the oil before a rash develops.
One method is to wash the infected area thoroughly with a strong soap; one of the more effective brands is Technu, which is available in most drugstores. Technu is designed to remove Toxicodendron oils and keep them from spreading. Archeologists, foresters, and others who spend a lot of time in the woods often make liberal use of it.
Urushiol can also be removed by swabbing it away with alcohol. However, it takes forever to do this effectively. For an area perhaps two inches diameter, you’ll need about a hundred cotton swabs and a bowl of 75-95% strength alcohol. Dip a swab into the alcohol, soak up some urushiol from your skin, and discard the swab immediately.
After you’ve done this 30 times, you can briefly rub the infected area with the alcohol-soaked swabs. After about 80 swabs, rub the area vigorously with the alcohol-soaked swabs in order to open the pores and retrieve any urushiol that’s entered them. This will also help sterilize the skin.
Other solvents can be used to remove the urushiol, but most of them — including gasoline, kerosene, and turpentine — do more harm than good.
Barrier creams are another common preventative. Most use clay-based ingredients to keep urushiol from contacting the skin altogether. It goes without saying that this material must be applied to every bit of exposed skin to be completely effective.
It should also be washed off within 4-6 hours in order to keep the skin safe. One brand, the Stockhausen Corporation’s Stokogard Outdoor Cream, seems to provide the best protection.
Attempts have also been made to produce a medication that, when taken in advance, can desensitize one to urushiol. For more than a half a century, tinctures containing tiny amounts of urushiol have been available commercially; however, overindulgence in these can be dangerous, and they’re rarely effective in any case.
Other, more effective medical preparations have been created, but their effects are neither universal nor lasting. In some cases, they’re actually deadly: sometimes allergen shots kill or severely incapacitate the people who receive them.
Fortunately, there’s some hope that current research into allergens will provide some clues that might eventually result in a true cure. Those of us who are sensitive can only wait and hope.
A Few Words of Warning
If you can avoid it, never burn poison ivy, oak, or sumac. The oils vaporize with the smoke, and can get into your eyes, mouth, nose, and lungs, not to mention infiltrate protective clothing. A high percentage of injuries among woodland firefighters can be attributed to urushiol inhalation.
Whatever you do, NEVER EVER eat any portion of any Toxicodendron plant in an attempt to desensitize yourself to urushiol. Despite the opinions of certain naturalists, this doesn’t work. There is no time of the year when Toxicodendron oils aren’t dangerous to the sensitized. The poison does nasty things to your outsides; can you imagine what it would do to your insides?
Remember this: no matter how bad an attack of Toxicodendron rash may seem, it’s almost never fatal and will go away within a few days. If you have any doubts about a remedy, avoid it. Poison ivy may not kill you, but some of the remedies can.