Summer is coming, our kids and pets will be playing outside enjoying the fresh air and sunshine, but lurking in the midst are some annoying summertime culprits. Take this time to refresh our memories and maybe learn something we didn't know about Poison Ivy, Sumac & Oak.

Cause
The rash caused by the plants poison ivy, poison sumac, and poison oak is an allergic reaction to the sap of these weeds. The sap, called urushiol oil, is clear or pale yellow, and escapes from damaged areas of the plant, no matter what time of year or whether the plant is dead or alive. Certainly a durable substance, urushiol can remain toxic on clothes and other objects for up to 5 years. Contact with an intact plant will not cause harm, but this is rare because poison ivy is extremely fragile, especially during the spring and summer months.

There are three ways to contact urushiol oil. You can touch a damaged plant directly, touch a contaminated object or animal, or expose yourself to airborne particles from burning or lawn mowing the plants. Urushiol oil is absorbed into the skin almost immediately, though washing with cold water and soap within 30 minutes of contact can help limit allergic reactions.

Contrary to what many people have been told, the rash caused by poison ivy is not contagious. Only exposure to urushiol sap will cause skin irritation, not contact with the skin of an infected person.

Symptoms
After contact with urushiol, sensitive individuals (about 85% of the population) will develop a rash within 48 hours. However, because sensitivity to the allergen develops with exposure – you are not born with it – first time contact may take up to 10 days to cause a rash. Any area of the body can develop the rash, though it is more likely in areas where skin is thin, such as the face. Affected areas will initially itch, and then become red, swollen, and blistered. In severe cases, patients develop oozing sores. There is a common misconception that scratching the rash causes it to spread. This is not true, but you should avoid scratching because it may cause scarring or secondary infection. It may seem like your rash is growing, but this is likely the result of varying skin thickness or multiple exposures to urushiol. The sap will be absorbed more slowly by skin that is thick, such as that found on the forearms, legs, and trunk.

After a few days, the rash may dry and begin to scale. Affected skin will not fully recover until all contaminated cells have been shed. This usually takes about 10 days.

Treatment
Fortunately, sensitivity to urushiol tends to decrease with age. But for those whose sensitivity causes them to suffer, here are some tips for treatment:

Wash exposed areas with cold water and soap as soon as possible. If you can do this within five minutes, the water may keep the urushiol from seeping into your skin. Even washing within the first 30 minutes will limit the severity of the rash. Hot water may open the pores to let the oil in.
Wash clothing and any objects that may be contaminated with urushiol, which can remain toxic for up to 5 years.
Soak in a bath of colloidal oatmeal or baking soda solution.
Cool compresses and ice can soothe itching temporarily
Cover affected areas with calamine lotion. Over-the-counter hydrocortisone creams are not strong enough to treat poison ivy rashes.
Take over-the-counter oral anti-histamines if itching is severe (if you do not experience adverse reactions from such medication).
For extreme cases, doctors can prescribe prescription-strength cortisone cream or oral steroids.

Prevention
The best prevention measure you can take is to learn how to identify the poisonous weeds. Unfortunately, this task is not as easy as the popular saying, “leaves of three, let them be,” makes it sound. A leaf of poison ivy or poison oak contains three pointed leaflets, and the middle leaflet has a longer stalk than the two side ones. However, even on the same plant the size and shape of the leaflets can vary. The edges of the leaves can be smooth or jagged, but are rarely lobed. Poison sumac, on the other hand, has leaves that contain 7-12 leaflets. The leaves of these plants tend to turn yellow or red in the fall even when other plants are still green. The berries of female plants change from green to off-white, and the leaves fall off before winter.

Another factor that makes identification difficult is the variety of forms poisonous plants may take. Poison ivy grows as a vine, climbing vine, or a low shrub; poison oak can be a short or tall shrub; and poison sumac is found as a tall shrub or small tree. In North America, the plants (in combination) are confined neither by geographical location nor by ecological community. Poison ivy likes fertile, well-drained soil; poison oak can grow in dry areas; and poison sumac prefers standing water. The weeds can be found anywhere in the continental U.S. (aside from some desert areas of Nevada).

Some tips to prevent developing a rash from poison ivy:
Learn what poison ivy, oak, and sumac look like so you can avoid them.
Destroy the weeds with herbicides in your own backyard, but be careful with dead plants because they still contain dangerous urushiol sap.
Wear long pants and long sleeves, boots, and gloves in areas where there might be poison ivy.
Do not let pets run through wooded areas, and wash them thoroughly if they might have touched poison ivy.
Do not burn plants you suspect are poisonous.
Barrier skin creams containing bentoquatam provide some protection by physically blocking the resin from reaching the skin. They are available over-the-counter.

Article courtesy of Princeton University.

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Poison Ivy, Sumac, and Oak
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