Why Do Poison Ivy, Poison Oak, and Poison Sumac Make You Itch?

Poison ivy, poison oak, and poison sumac grow abundantly in many areas across North America. The plants can be a significant concern for many people from hikers to children playing in their own backyard. The key is being able to identify the plants and avoid them. However, this is not always possible. For this reason, it is important to understand why the plants make you itch, quickly identify an allergic reaction from contact with the plants, and treat it properly.

Differences Between the Plants

Before examining the "itchy" factor of these plants, let's discuss where they are found and how to tell them apart. According to the USDA Plants Database, Poison ivy, poison oak, and poison sumac are all members of the Toxicodendron plant genus. While the plants are all closely related, there are several differences in their physical appearance and regions where they are found.

Poison ivy is the most common of the group and is famous for being easily identified by having clusters of three almond-shaped leaves . It is found widely in wooded areas across eastern and central North America. The plant often grows as a vine and can usually be found climbing the trunks of trees and sides of buildings.

Poison oak is also a vine and can be found in the eastern and western coastal areas of North America. The plant's leaves, which closely resemble that of the White Oak tree, grow in clusters similar to poison ivy.

Unlike poison ivy and poison oak, poison sumac grows in the form of a shrub or bush. It primarily grows near marshes and swamps in the eastern United States and Canada.

Why Does it Make you Itch?

While there are several differences between poison ivy, poison oak, and poison sumac, all three contain the same oily toxin that causes a skin irritation. The toxin, urushiol , causes an itchy rash that is typically identified by red, blistery patches on the skin. Irritation can be caused by direct contact with urushiol-containing plants. It is also possible to come in contact with the toxin indirectly by touching objects such as clothing, shoes, or pets that have come in contact with urushiol.

Treatment of the Rash

According to American Academy of Dermatology, rash symptoms can last from a few hours up to two weeks depending on the extent of contact and an individual's sensitivity to the toxin. First, wash any areas of skin that may have come in contact with the plants. This will rid the skin of excess urushiol residue and prevent it from spreading to other areas of the body. Apply a cool washcloth to inflamed area to help reduce the itchy feeling. Antihistamine pills, such as Benadryl, or a calamine lotion may help to reduce the effects of the allergic reaction.

How to Get Rid of Poison Ivy, Oak, and Sumac Plants

The absolute best way to get rid of poison ivy, poison oak, and poison sumac are to pull the plants by the roots and dispose of them. Before tackling this task, be sure to wear a long sleeve shirt or jacket, long pants, and heavy duty gardening gloves to prevent getting plant toxin on your skin. Grab the base of the plant firmly and pull. Poison ivy, poison oak, and poison sumac are also susceptible to most weed killers. However, be careful as these will usually kill other plants in the spray area.