Poison sumac is a woody shrub or small tree found primarily in swampy areas of the eastern United States. Contact with the plant causes allergic contact dermatitis in most people. This severe allergic skin reaction is triggered by urushiol, an oil present in all parts of the plant, including the leaves, stems, and roots. Even when the plant appears dormant and loses its leaves, the risk of exposure remains high year-round.
The Persistence of Urushiol
The continued threat of poison sumac during the winter is due entirely to the remarkable chemical stability of urushiol. This oil is extremely resilient to environmental degradation. Urushiol does not evaporate with cold, nor does it freeze or degrade significantly when the plant loses its foliage or dies. It can remain active and capable of causing dermatitis for months, or even years, on dead plant matter.
This persistence means that contact with any part of the dormant plant, or anything the plant has contaminated, is a significant danger. The oil can adhere to surfaces like clothing, tools, and pet fur, creating a risk of secondary exposure long after the initial contact. Even minimal contact with contaminated surfaces can cause a skin reaction in sensitive people.
Identifying the Dormant Plant
Identifying poison sumac during winter requires focusing on its woody structure rather than its absent leaves. The plant typically grows as a multi-stemmed shrub or small tree, often reaching heights up to 20 feet. It is distinctly different from the vine-like structure of its relative, poison ivy.
A key identifying feature of the dormant poison sumac is its stems and leaf stalks, which frequently retain a bright red color. Although the leaves are gone, their former attachment points may be visible. During the growing season, the leaves appear in clusters of seven to fifteen leaflets.
Another strong visual cue is the presence of its fruit, which often persists through the fall and winter months. These smooth, greenish-white to gray fruits hang in loose, elongated clusters from the bare branches. Finding these pale berries in the swampy or wet areas where poison sumac thrives is a strong indicator of the plant’s presence.
Common Winter Exposure Routes
Exposure to urushiol during the winter often occurs through activities that involve handling or disturbing the dormant plant’s woody stems. Brush clearing and trail maintenance are common activities that can inadvertently break the stems, releasing the oil onto skin or clothing. Since the plant is harder to spot without its leaves, people often contact it unknowingly while working in wooded areas.
A significant winter exposure risk comes from handling firewood. If poison sumac stems or roots were cut along with the wood, the urushiol remains on the bark and can easily transfer to hands, clothing, and tools. Tools used for yard work or woodcutting can harbor the oil for years if not properly cleaned, leading to delayed or repeated exposure.
Burning Debris
The most dangerous route of winter exposure is through burning debris that includes poison sumac. When the wood or stems are burned, the urushiol becomes airborne on smoke particles. Inhaling this smoke can cause severe irritation and inflammation in the nasal passages, throat, and lungs, requiring immediate medical attention.
Preventing Secondary Exposure
To prevent secondary exposure, any clothing or equipment that has contacted the plant should be washed separately with hot water and detergent immediately after use.