 |
|
| ||||||||||||||||||||||||||
|
|
| ||||||||||||||||||||||||||
|
|
|
|
|
| ||||||||
This page is about the plant; for other meanings, see Poison ivy (disambiguation).
| Poison Ivy | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Scientific classification | ||||||||||||||
| ||||||||||||||
| Binomial name | ||||||||||||||
| Toxicodendron radicans |
Poison ivy (Toxicodendron radicans), in the family Anacardiaceae, is a woody vine that is well-known for its ability to produce urushiol, a skin irritant which for most people will cause an agonizing, itching rash.
Poison ivy grows vigorously throughout much of North America, but particularly in the American Midwest. It can grow as a shrub up to about four feet tall, or as a groundcover four to ten inches high, or as a climbing vine on any and every support. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.
Poison ivy is apparently far more common now than when the Europeans first entered North America, because it has profited immensely from the "edge effect", enabling it to form lush colonies in such places.
The leaves are compound with three leaflets, giving rise to the doggerel, "Leaflets three, let it be." The berries (actually drupes) are a grayish-white color and are a favorite winter food of some birds.
Poison ivy looks like ivy. Each tendril of ivy ends in three leaves which are almond shaped. Color ranges from light green (usually the younger leaves) to dark green (mature leaves). Leaves can be as long as 10 or 12 inches long, but are usually 4-6 inches long when they are mature. Each leaf has a FEW teeth along its edge, and the leaf surface is SMOOTH. To compare, blackberry and raspberry leaves also come in threes, but they have MANY teeth along the leaf edge, and the top surface of their leaves are very wrinkled where the veins are. The stem and vine are smooth, brown and woody, while blackberry stems are green with thorns.
Virginia creeper, Parthenocissus quinquefolia, vine can look like poison ivy. The younger leaves can come in groups of three but have a few more serrations along the leaf edge, and the leaf surface is somewhat wrinkled. Virginia creeper and poison ivy very often grow together, even on the same tree.
Poison oak leaves also come in threes on the end of a stem, but each leaf is shaped somewhat like an oak leaf. True poison oak only grows in the western United States, although many people will refer to poison ivy as poison oak. This is because poison ivy will grow in either the ivy-like form or the brushy oak-like form depending on the moisture and brightness of its environment. The ivy form likes shady areas with only a little sun, and tends to climb the trunks of trees, and can spread rapidly along the ground.
If the poison ivy is growing up a tree look at the vine. It will be smooth with no ladder like roots clinging to the tree. (Some sources report that poison ivy does have these ladder like roots.)
Beware of dead poison ivy: it still has plenty of urushiol, and will give the same effect. Compare the thick vines of grape: no rootlets visible, to the vines of poison ivy: so many rootlets that the stem going up a tree looks furry.
The skin rash, featuring fluid-filled blisters and reddened areas that itch intensely, is caused by an irritating oil, urushiol. Urushiol binds to skin cell walls, changing their configuration, so that the body's immune system no longer recognizes these cells as belonging to the body and attacks them as foreign. Some people are susceptible to the rash, and others aren't, but reactions can change during a person's lifetime. Someone who was formerly not subject to it may become very sensitive, and vice versa.
Normally, it takes about twenty-four hours for the rash to first appear, though it may worsen during the next few days and may appear to spread, when in fact what is happening is that areas that received a lesser dose are latently reacting. The rash takes one to two weeks to run its course, but normally does not leave scars. Severe cases will have small (1-2mm) white fluid-filled blisters on the skin.
When a person has been in contact with poison ivy, there are several measures that may be taken to prevent or lessen a rash. and Tecnu are commercial preparations designed to 'unlock' urishiol from the skin. If applied within 20 minutes of exposure to poison ivy, these may be effective in completely preventing an outbreak. Zanfel, the more expensive of the two by far, is said to be effective at any stage of a poison ivy outbreak. Once an outbreak has occurred, using ice will dull the pain.
Most poison ivy rashes will self-resolve within 14 days without treatment. If the rash is severe or if it doesn't resolve within 14 days, see a doctor.
Most people find that cool compresses in one form or another are quite soothing. Try using a towel or wash cloth soaked in either plain tap water or Burow's Solution (an astringent solution -- you can make it yourself using Domeboro tablets or powder packets available over-the-counter). This can help relieve the intense itching and remove dry crust that has formed as a result of the rash. A fan blowing over the cool compress will diminish some of the heat of the itching and help to dry up some of the ooze coming from the rash. As the skin is cooling, the blood vessels compress and that cuts down on the itching and the new ooze. This is especially good during the two or three worst days of the rash. Along the same lines, some dermatologists recommend rubbing an ice cube gently over the rash several times a day, then letting the skin air dry. Soaking in a tub, particularly using an oatmeal bath such as Aveeno, can also be very soothing to the itch. Be sure the bath is cool or lukewarm -- but not hot -- as heat tends to make the rash even more inflamed.
After the cooling (using any of the forms mentioned above) coat the rash with a shake lotion such as calamine. This continues to relieve the itching and helps to dry up the blisters. Be sure to check the expiration date on an old calamine bottle in your medicine cabinet, since it may not be effective after the expiration date. Be sure the shake lotion does not contain benzocaine, zirconium, or a topical antihistamine, such as benadryl. These can actually make the rash worse by producing their own allergic reactions when applied to already sensitive skin.
Smearing on hydrocortisone, or other topical corticosteroids, will help suppress the itching and give temporary relief, but does little to hasten the drying up of the rash. Similarly, taking an oral antihistamine, such as benadryl, can help with the itching quite a bit, although it does not speed up resolution of the rash. Taking benadryl at nighttime will make most people drowsy and help them sleep through the night without itching. Again, don't use benadryl cream or spray topically, because this can cause its own reaction.
The goal of reducing itching is brought about by cooling (by restricting the blood vessels), by drying the rash, or by quieting down the allergic response.
In severe cases of poison ivy, poison oak, or poison sumac it is a good idea to see a doctor. Sometimes large blisters need to be drained, and sometimes an oral steroid such as prednisone may be useful. Systemic steroids produce rapid resolution of both the itching and the rash. If they are needed, a gradually tapering dosage over about 12 days should be given. The dosage needs to be tapered to avoid side effects after discontinuing use, and the entire course should be taken since stopping earlier may result in a rebound rash as bad as the original.
Allergy shots are available to help prevent recurrences of the poison ivy, poison oak, or poison sumac rash. Unfortunately, the shots for this are frequently ineffective and should be reserved only for those who are extremely sensitive. Prescription pills containing small amounts of extract from the plants have been used for immunization. However, these pills can cause uncomfortable side effects. The pills are recommended only if given before contact with the plant and only for individuals who come into frequent contact with the plant. Using topical creams (such as Ivy Shield, IvyBlock, Hollister Moisture Barrier, Stokogard Outdoor Cream, or Hydrophil) can also help protect against contracting the rash.
One traditional remedy is to find plants of jewelweed, Impatiens species, and to take the whole plant, crush it into a ball, and vigorously rub it into the exposed area. Or, crush some jewelweed stems in a container, and use a cotton ball to soak up the juice. Spread it on the rash as soon as possible.
An unfortunate story, often repeated, is that "Wherever poison ivy is found, jewelweed grows close by." This is completely untrue; poison ivy grows in a wide variety of habitats, while jewelweed is restricted to moist bottomlands and valleys with rich soil. The reverse is true — wherever jewelweed is found, poison ivy is usually close by. Jewelweed grows in sunny wet areas, like ditches on the roadside. The 1 cm (1/2 inch) long flowers are shaped like a shoe. Some plants have orange flowers with dark spots. Some plants have plain yellow flowers.
Another method is to take mud, preferably clay mud, and vigorously rub it in. Affected people can also use either laundry detergents or strong soap to scrub the area before the rash appears.
Other home remedies include: acorn tea, birch tea, bulrush, burdock, cattail, chicory, comfrey, hemlock, milkweed, mint, spicebush, sumac (non-poison), sweet fern, thistle tea, and yucca.
Urishiol is an oil and is not washed off by plain water. People have had success in lessening the rash by wiping the area clean with alcohol, or mild soap, in order to break down the oil. However, laundry detergent or Fels-Naphtha soap work much better, but vigorous rubbing is necessary. If you are desperate, you could also try wiping the area with other solvents, like acetone (nail polish remover). Some article advise against this because it will deprive your skin of moisturizers to protect you from the oil. However, the oil is obviously having an effect on your skin, and you can always put lotion on the area later.
One treatment is steroids, as a shot or pills, to control the itching. Another treatment is calamine lotion over the affected area, apply as needed. Other topical treatments include: liquid Benedryl or any other anti-itch cream/oil. A bath with baking soda also helps some people. Soak in a warm (not hot) bath for 30 minutes. Using a hot bath would cause one's pores to open and let more urushiol attack the skin.
Preventing exposure to poison ivy involves ways of preventing the oil from getting on the skin. - Wear long clothing, avoid any plants that look like poison ivy. - If you must wear short clothing, put thick lotion on areas that may be exposed to poison ivy, like the legs. A suntan oil may work even better. - If you handle tools that have touched it, wear gloves, then wipe the tools with alcohol immediately after using them, or throw them away.
A rash from poison ivy or oak is not at all contagious. People get the rash from oil that gets on their skin from the plants. BUT, until the oil is removed, they are contagious whether or not they have a rash. Generally, all the urushiol binds to skin cells within about twenty-four hours.
The oil can be removed by washing in warm soapy water. Catching poison oak or ivy from swimming in a pool is very unlikely. Pool water might wash the oil off and someone else could get it by touching the oil in the water, but the exposure would be tiny and would likely be removed by further swimming or by showering after the swim.
So why does the rash spread?
There are three reasons that the rash spreads.
Until people exposed to poison ivy take a bath or shower, any place they touch will spread the oil that causes the rash. The rash can spread by touching the oil on their own hands, their clothes, or can even be spread by touching a dog, if that dog has the oil on its hair.
The second reason the rash spreads has to do with variable amounts of oil and variable protectiveness of skin. Wherever you get the most oil, on the most vulnerable area of skin, will break out first. Where the skin is thicker or there is less oil, the rash may not appear until several days later -- so it only appears to be spreading. Eczema patches are especially vulnerable to poison ivy.
The third reason that poison ivy rashes spread is that the red itchy rash is caused by a histamine release in the skin. Scratching releases more histamine and can make the rash spread setting up an itch-scratch-itch cycle.
The good news is that when the rash turns to blisters and the blisters pop, that honey-colored liquid and honey-colored crust is not contagious at all.
Poison ivy is EXTREMELY hardy and very resistant to poisons. Some herbicides will not destroy the roots, allowing the plant to grow back the following year. Roundup and other grass killers do not affect poison ivy. Some people recommend using a brush killer.
You can also physically pull up all the vines and roots but you must wear gloves and pants and a long sleeve shirt. DO NOT BURN poison ivy. The smoke particles carry the irritant and allow it to be inhaled; people that are extremely sensitive to poison ivy could die. Wrap the plants in a good garbage bag and bury them or dispose of them in a landfill.
Another solution is mixing 1/4 cup salt in 1 quart of water and put in a spray bottle. Spray the leaves of the poison ivy with this solution. NOTE: this will possibly kill any surrounding plant life if it gets a significant amount of salt water on it.
Yet another solution which has worked is sprinkling Borax on the leaves. It will take about 3 weeks for the leaves to die back. It may be necessary to repeat this treatment for more than one growing season.
|
||||
| View Live Article | This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License | |
||
