For instigating blisters, rashes and general discomfort, few plants can compete with poison ivy. Although a fortunate few persons are immune to poison ivy's deleterious effects, some 70 percent of the population experience physical reactions after coming in contact with it.
Poison ivy has been irritating people for a long time. In 1609, English adventurer John Smith gave the plant its apt name. He thought it resembled English ivy in appearance, but went on to observe that the plant "causes abominable itchynge."
Found from the East Coast to the West Coast and from southern Canada to Mexico, the plant grows throughout Idaho and in every type of terrestrial habitat. Preferred habitats include forest edges and recently disturbed fields.
The shape, color, and texture of poison ivy leaflets vary. Poison ivy's trademark leaf triads are reddish when they first appear in the spring, but turn green during the summer. Although the color of its berries is sometimes mentioned as a way of identifying the plant, this is not as reliable as leaf identification.
Poison ivy fruits are clusters of seeds with a pale yellow rind. The fruit contains the chemical irritant urushiol, but that does not stop birds from eating them. Typically, the seeds pass through avian digestive tracts unharmed.
Urushiol is far more problematic for humans. Poison ivy rash involves allergic dermatitis caused by contact with the substance. Urushiol is a colorless oil that oozes from any cut part of the plant. Simply brushing against a plant may not cause a reaction. But, a person may develop dermatitis without ever coming into direct contact with poison ivy. Virtually invisible, urushiol can be carried on the fur of animals, garden tools or on any object that has come into contact with a cut plant.
Once it touches human skin, urushiol begins to penetrate. Individuals who are highly sensitive to the chemical will experience a reaction in the form of a linear rash. Blisters and severe itching will follow swelling.
The severity of reaction varies from person to person. Severe reactions include swelling in the throat, dizziness, weakness, and breathing problems. If you experience extreme itching or the exposure involves the eyes, throat or lungs, seek medical attention. And remember: you can have an allergic reaction to poison ivy even if you never leave your house. Anything or anybody that has come into contact with the plant can spread it.
Contrary to popular belief, you cannot get a poison ivy rash from someone else's blisters. The liquid inside your blisters is not urushiol but fluids your body has produced in an attempt to prevent the worst effects of exposure.
The best preventive for poison ivy is to avoid it. Don't touch the plant. Never grab leaves along a trail or fence. If you must walk through poison ivy, step on the plants with the sole of your shoes.
If you have had a brush it, wash all exposed areas of your body with running water as soon as you can reach a stream or garden hose. If you do this within five minutes of exposure, the water will deactivate the urushiol and keep it from spreading to other parts of the body.
After returning home, wash all clothing outside with a garden hose before bringing it into the house, where resin can be transferred to rugs or furniture.
If you do develop a rash, avoid scratching the blisters. Cool showers will help ease the itching, and over-the-counter preparations, such as calamine lotion, may help relieve mild rashes.
In severe cases, a physician may prescribe a steroid cream containing hydrocortisone to be applied to poison ivy lesions four to six times a day. Poison ivy can be controlled in lawns and pastures with Banvel or Crossbow. These chemicals should not be sprayed near or under sensitive trees, ornamentals or garden species.
Even if poison ivy grows in an area where people could come in contact with it, a prominently displayed warning sign may be the most practical measure.
Although poison ivy causes many of us discomfort, the plant does have some merit. For example, many birds eat poison ivy berries. Rabbits, deer, and other animals eat the fruit with no ill effects. Thick stands of poison ivy provide cover for small wildlife, and the plant's ability to thrive in disturbed habitats makes it valuable in protecting soil from erosion.
Poison ivy doesn't have to get under our skin. With a few preventive measures, we can easily identify and avoid the plant. We can learn to coexist with poison ivy and even respect it as another fascinating aspect of Idaho's natural beauty.
Mary Syrett is a freelance writer and student of the natural world. Articles written by her have appeared in both national and regional publications.