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Photo by Sharon Dominick/Getty Images, (right) Ed Reschke/Getty Images

Published September 2, 2015

Outdoor enthusiasts and gardeners alike know all too well the itchy or red skin rash caused by poison ivy. The prevalence of this pesky plant has led the TOH staff to wonder: Is poison ivy more potent this year?

Scientists and poison-ivy removal professionals pondered this question at the third annual Philadelphia Poison Ivy Conference this summer. They met to collaborate on ways to identify the plant, remove it, and prevent it from growing.

Since there is much folklore about this pervasive, harmful plant, we consulted the experts at the American Academy of Dermatology (AAD), the Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC) to separate the myths from the facts. Read on for help in identifying poison ivy in your yard and ways to prevent exposure.

Myth 1: Poison ivy is getting stronger and is more potent than it was in the past.

Fact: This theory is being researched, but more evidence is needed to support it. In June, CBS News reported that poison ivy—and poison oak and poison sumac—might be getting stronger over time as a result of increased carbon dioxide in the atmosphere.

About 85 percent of people are sensitive to urushiol, the sap oil in poison ivy, and will develop a rash. The other 15 percent will never develop a rash. However, the AAD notes that a rash may not occur at all after a person's first exposure to poison ivy. But after the second exposure, the 85 percent who are sensitive will develop a rash and will again develop a rash after each exposure. While the experts are researching whether the plant itself is stronger, a sensitive person's reactions can become worse overtime.

Myth 2:

You can identify poison ivy by seeing a group of three green leaves.

Fact: Yes, three leaves are most common. However, the CDC warns that the shape and the number of leaves may vary depending on the species, the local environment, and the season.

For instance, Eastern poison ivy appears as a hairy, rope-like vine with three leaves budding from one stem, while Western poison ivy appears as a low shrub with three leaves. Like most foliage, the leaves change color each season, says the FDA: reddish in spring, green in summer, and yellow, orange, or red in fall.

Myth 3: Your skin must come into direct contact with the plant itself in order to develop a rash.

Fact: An allergic reaction will occur if a person comes in direct contact with the sap oil (urushiol) on a plant or on any surface, from yard tools to a pet's fur to clothing. The oil can linger on almost any surface for up to five years! Even fallen leaves are still active.

To protect yourself from both direct and indirect contact, always wear long sleeves, pants, boots, and nonpermeable gloves. It is best to wash exposed clothes separately and to clean yard tools with rubbing alcohol or soap and water.

Do not dispose of poison ivy plants by burning them! Inhaling the smoke can cause severe allergic respiratory problems.

Myth 4: A poison-ivy rash can spread to other parts of your body or onto another person from skin-to-skin contact or through weeping blisters.

Fact: Because the blisters do not contain urushiol, you can't spread the rash to other parts of your body or to others through contact with them—as long as the skin is cleaned after exposure. Use a topical hydrocortisone cream, calamine lotion, or oatmeal baths to reduce the itching and blistering. If you think your rash is severe, consult a dermatologist right away.

If there is a poison-ivy invasion in your yard or garden, follow This Old House landscape contractor Roger Cook's advice on how to get rid of it safely: How to Clear Poison Ivy