Poison ivy, poison oak, and poison sumac are the most common cause of allergic reactions in the United States. Each year 10 to 50 million Americans develop an allergic rash after contact with these poison plants, a rash that and can affect almost any part of the body.
In the West, this plant may grow as a vine but usually is a shrub. In the East, it grows as a shrub. It has three leaflets to form its leaves' "hairs."
In the East, Midwest and South, it grows as a vine. In the far Northern and Western United States, Canada and around the Great Lakes, it grows as a shrub. Each leaf has three leaflets.
Grows in standing water in peat bogs in the Northeast and Midwest and in swampy areas in parts of the Southeast. Each leaf has seven to 13 leaflets.
Poison Plant rash is an allergic contact dermatitis caused by contact with oil called urushiol. Urushiol is found in the sap of poisonous plants like poison ivy, poison oak, and poison sumac. It is colorless or pale yellow oil that oozes from any cut or crushed part of the plant, including the roots, stems, and leaves. After exposure to air, urushiol turns brownish-black. Damaged leaves look like they have spots of black enamel paint making it easier to recognize and identify the plant. Contact with urushiol can occur in three ways:
- Direct contact - touching the sap of the toxic plant.
- Indirect contact - touching something on which urushiol is present. The oil can stick to the fur of animals, to garden tools or sports equipment, or to any objects that have come into contact with it.
- Airborne contact - burning poison plants put urushiol particles into the air.
When urushiol gets on the skin, it begins to penetrate in minutes. A reaction appears, usually within 12 to 48 hours. There is severe itching, redness, and swelling, followed by blisters. The rash is often arranged in streaks or lines where the person brushed against the plant. In a few days, the blisters become crusted and take 10 days or longer to heal. The rash does not spread by touching it, although it may seem to when it breaks out in new areas. This may happen because urushiol absorbs more slowly into skin that is thicker such as on the forearms, legs, and trunk.
Prevention of Poison Ivy
Prevent the misery of poison ivy by looking out for the plant and staying away from it. You can destroy these weeds with herbicides in your own backyard, but this is not practical elsewhere. If you are going to be where you know poison ivy likely grows, wear long pants, long sleeves, boots, and gloves. Remember that the plant's nearly invisible oil, urushiol, sticks to almost all surfaces, and does not dry. Do not let pets run through wooded areas since they may carry home urushiol on their fur. Because urushiol can travel in the wind if it burns in a fire, do not burn plants that look like poison ivy
Barrier skin creams such as a lotion containing bentoquatum offer some protection before contact with poison ivy, poison oak, or poison sumac. Over-the-counter products prevent urushiol from penetrating the skin. Ask your dermatologist for details.
If you think you've had a brush with poison ivy, poison oak, or poison sumac, follow these simple steps:
Wash all exposed areas with cold running water as soon as you can reach a stream, lake, or garden hose. If you can do this within five minutes, the water may keep the urushiol from contacting your skin and spreading to other parts of your body. Within the first 30 minutes, soap and water are helpful.
Relieve the itching of mild rashes by taking cool showers and applying over-the-counter preparations like calamine lotion or Burow's solution. Soaking in a lukewarm bath with an oatmeal or baking soda solution may also ease itching and dry oozing blisters. Over-the-counter hydrocortisone creams are not strong enough to have much effect on poison ivy rashes.
Prescription cortisone can halt the reaction if used early. If you know you have been exposed and have developed severe reactions in the past, consult your dermatologist. He or she may prescribe cortisone or other medicines that can prevent blisters from forming. If you receive treatment with a cortisone drug, you should take it longer than six days, or the rash may return.