Poison Ivy

Every year Manitoban doctors see large numbers of vacationers who have become exposed to poison ivy. Poison ivy rashes can range from small nuisances to severe discomfort.

The poison ivy rash is a hypersensitivity reaction to urushiol oil in the leaves of the Rhus plants. In Manitoba we have poison ivy ( Toxicodendron radicans) but poison oak in Ontario is very similar.

Inanimate objects including pet's hair can also spread the oil. People also get poison ivy rashes trying to uproot these plants as roots and vines also contain urushiol.

The plant oil gets onto skin and is contagious for a short time where it can be spread to others or elsewhere on the body. It is during this time that washing with alcohol or water will be most useful in preventing a rash.

After this, people sensitive to the urushiol develop a delayed hypersensitivity rash.

This contact dermatitis involves itchy and painful rashes wherever the oil was spread and may later “weep” as they exude clear fluid. The reaction intensity depends on how much oil was involved and how sensitized to oil that person is. Very small exposures can cause “new” rashes up to 2 weeks later, so the late appearance of some parts of the rash do not mean it is spreading. Rashes disappear after 1-3 weeks but in severe cases people need relief.

Burning plants can even transmit the oil in smoke. Fire fighters exposed to forest fire smoke have developed poison ivy irritation in their lungs!

Mild symptoms may be treated with cool compresses, calamine lotion and Aloe vera (either the plant itself or a cream) which work very well. Often over the counter hydrocortisone creams may be too weak to help much.

In my office I see people with moderate to severe symptoms so I prescribe a cortisone cream if the rash is localized or oral corticosteroids (prednisone) for severe cases.

Short-term use of prednisone is a reasonable and safe treatment but much longer term use can lead to side effects so this treatment is always individualized.

Weeping rashes should be kept clean and watched for superinfection.

As awful as poison ivy looks and feels- once the rash has started it is not contagious to others or yourself since the oil is not present and all the redness is from irritated skin.

The best way to deal with poison ivy is by avoiding it.

The plant is a 3-leafed vine with white berries and leaves that vary in size and colour (green to orange, red or bronze). Identifying the plant is difficult, as it may appear different through the year.

Many websites have pictures such as Agriculture Canada http://res2.agr.gc.ca/ecorc/poison/radicans_e.htm . Everyone going camping should familiarize themselves with the diverse appearances of poison ivy.

If you aren' t sure- avoid all strange 3-leafed plants!

"Leaves of three, let it be; berries white, poisonous sight."