Poison Ivy

What causes the poison ivy rash?

Poison ivy rash is an allergic contact rash (dermatitis) caused by contact with an oil called urushiol (you-ROO-shee-ol). Urushiol is found in the sap of poison ivy, poison oak and poison sumac. It is a colorless or pale yellow oil that oozes from any cut or crushed part of the plant, including the roots, stems and leaves.  You may develop a rash without ever coming into contact with poison ivy, because the urushiol is so easily spread.  Contact with urushiol can occur several ways:

Direct contact - touching the sap of the toxic plant.

Indirect contact - touching something to which urushiol has spread. 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 a crushed or broken plant.

How does the poison ivy rash develop?

Once urushiol touches the skin, it begins to penetrate in minutes. In those who are sensitive, a reaction appears as a line or streak of rash, usually within 12 to 48 hours. Redness and swelling occur, often followed by blisters and severe itching. In a few days, the blisters may become crusted and begin to scale. The rash takes 10 days or longer to heal.

The rash can affect almost any part of your body, especially where your skin is thin, such as on your face. A rash develops less often on the soles of your feet and palms of your hands, where the skin is thicker. The rash does not spread, although it may seem to when it breaks out in new areas.

Who is sensitive to poison ivy?

We are not born with sensitivity to poison ivy. It develops only after several encounters with the plants, and sometimes over many years. Studies have shown that approximately 85 percent of the population will develop an allergic reaction if exposed to poison ivy. Although they are not sure why, scientists believe that an individual's sensitivity to poison ivy changes with time and tends to decline with age. The first bout of poison ivy usually occurs in children between the ages of 8 and 16

What do poison ivy, poison oak and poison sumac look like?

Learn to identify the poison ivy plant, and you will have taken the first step in avoiding poison ivy. The popular saying "leaves of three, beware of me" is a good rule of thumb for poison ivy and poison oak but is only partly correct. A more exact saying would be "leaflets of three, beware of me" because each leaf has three leaflets. Poison sumac, however, has a row of paired leaflets. On each of these plants, the middle or end leaflet is on a longer stalk than the other two or more leaflets. This differs from many other look-alikes.

What To Do About Poison Ivy?

Prevent the misery of poison ivy by looking out for the plant when you are outdoors 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 and long sleeves, boots and gloves. Remember that the plant's nearly invisible oil -- urushiol -- sticks to almost all surfaces. Do not let pets run through wooded areas since they may carry home urushiol on their fur.

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 will neutralize or deactivate the urushiol in the plant's sap and keep it from spreading to other parts of the body. Soap is not necessary, and may even spread the oil.

What is the treatment for the poison ivy rash?

Barrier skin creams such as a lotion containing bentoquatum (IvyBIock offers some protection before contact with poison ivy, poison oak or poison sumac. This over-the-counter product prevents urushiol from penetrating the skin.

Over-the-counter preparations, like calamine lotion will relieve mild rashes. Soaking in a lukewarm bath with an oatmeal or baking soda solution is often recommended to dry oozing blisters and offer some comfort. Cool showers will help ease the itching. In severe cases, prescription corticosteroid drugs can halt the reaction if taken soon enough. If you know you've been exposed and have developed severe reactions in the past, be sure to consult your pediatrician.

Common Myths About Poison Ivy

Scratching poison ivy blisters will spread the rash. False.

The fluid in the blisters will not spread the rash. Before blisters form, the rash is spread by urushiol on your hands, for instance, by scratching your nose or wiping your forehead. Avoid excessive scratching of your blisters. Your fingernails may carry bacteria that could cause an infection.

Poison ivy rash is "catching." False.

The rash is a reaction to urushiol. The rash cannot pass from person to person; only urushiol can be spread by contact.

Once allergic, always allergic to poison ivy. False.

A person's sensitivity changes over time, even from season to season. People who were sensitive to poison ivy as children may not be allergic as adults.

Dead poison ivy plants are no longer toxic. False.

Urushiol remains active for up to several years. Never handle dead plants that look like poison ivy.

Rubbing weeds on the skin can help. False.

Usually, prescription cortisone preparations are required to decrease the itching.

One way to protect against poison ivy is by keeping yourself covered outdoors. True.

However, urushiol can stick to your clothes, which your hands can touch and then spread the oil to uncovered parts of your body. For uncovered areas, barrier creams are sometimes helpful. Learn to recognize poison ivy so you can avoid contact with it.