Poison sumac (Toxicodendron vernix) contains a rash-inducing oil called urushiol. When this colorless, oily resin makes contact with skin, it can cause allergic contact dermatitis.Poison sumac rashes have red blotches of inflammation or clusters of blistery skin that itch.
The urushiol oil that causes poison sumac rash is also found in poison ivy and poison oak. All three plants are part of the Toxicodendron genus. The leaves, stems, flowers, and roots of these poisonous plants can cause itchy Toxicodendron dermatitis. However, poison sumac rash is often more severe than those caused by poison ivy or oak.
Read on to learn what you need to know about what poison sumac rash looks like, how to prevent it, the three typical poison sumac rash stages, and the best poison sumac treatment options.
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What Are the Symptoms of Poison Sumac?
Plant dermatitis from contact with a rhus tree.
Reproduced with permission from © DermNet dermnetnz.org 2023.
Common symptoms experienced by individuals with poison sumac rash include:
- Itchy skin (pruritus)
- Inflammation
- Skin swelling
- Burning sensations
- Red streaks or blotches
- Raised bumps
- Fluid-filled blisters that may “weep”
How Common is Poison Sumac Allergy?
Roughly 50% to 75% of the U.S. population is allergic to the urushiol oil found in poison ivy, oak, and sumac.
If the oil from poison sumac is thoroughly removed within 10 minutes of contact, it usually will not cause a rash. However, if it remains on the skin for longer than 10 minutes, rash symptoms such as itchy skin, red streaks, and patches of fluid-filled blisters typically appear within eight to 48 hours. Poison sumac rash is self-limiting, meaning it heals itself, and usually resolves in under a month.
There is no cure for poison sumac rash, but the following home remedies can relieve symptoms:
If the poison sumac rash is severe, a healthcare provider may prescribe oral steroids such as prednisone or stronger topical steroid cream than is available over the counter, without a prescription.
How to Identify Poison Sumac
Poison sumac looks like a woody shrub or small tree. A full-grown poison sumac tree can be 20 feet tall. This plant is identifiable by its seven to 13 leaflets arranged in even pairs with one solo leaflet sticking off the stem’s end. In June and July, poison sumac has yellowish-green flowers. By September, grayish-white berries can be seen dangling.
Poison sumac trees require excessive wetness and thrive in flooded soil found in marshes, swamps, or peat bogs. Poison sumac often grows along pond edges or riverbanks with the tree’s roots visibly immersed in shallow water.
Even when environmental conditions are hospitable to poison sumac, it’s still fairly rare. Poison sumac is native to the eastern United States and rarely found west of the Mississippi River except in the states of Texas, Louisiana, or Minnesota. If the soil is dry or the climate is arid, it’s unlikely that you’ll encounter poison sumac.
Similar Plants
Poison sumac isn’t like other nonpoisonous sumac plants is similar other poisonous plants that belong to the Toxicodendron genus such as poison ivy and poison oak. AllToxicodendron plants such as poison sumac, poison ivy, and poison oak contain the same urushiol oil that causes a skin rash known as urushiol-induced contact dermatitis or Toxicodendron dermatitis.
What to Do If You Are Exposed to Poison Sumac
If you are exposed to poison sumac, the first thing to do is get the plant’s rash-inducing urushiol oil off your skin. Urushiol is a transparent substance that sticks to the skin and can easily get smeared without leaving any visible traces until the rash appears. Oil-dissolving solvents such as isopropyl alcohol or dish soap work best when removing the urushiol oil that causes poison sumac rash from the skin.
If effectively removed within 10 minutes of skin contact, urushiol won’t likely trigger an allergic reaction. Be sure to wash any area of your body that may have come into contact with poison sumac, as well as clothing and shoes. Wear vinyl or cotton gloves when handling items that touched poison sumac, and avoid latex gloves as the oil can penetrate the rubber. Pets can also spread poison sumac oil, so be sure to bathe them with gloved hands if they have been in an area with it.
The rash and watery blisters associated with poison sumac are not contagious once the urushiol oil is gone. However, if the oil lingers on clothes, shoes, gardening gloves, and outdoor tools, it can stay active for up to five years and cause an allergic skin reaction long after contact with the poison sumac shrub or tree.
3 Stages of Poison Sumac Rash
Poison sumac rash usually develops in the following three stages:
- Itchy skin without noticeable inflammation or discoloration.
- Reddish streaks or blotches appear as itchiness persists.
- Fluid-filled blisters form in clusters where the skin absorbs urushiol oil.
When to Contact a Healthcare Provider
As with other severe forms of urushiol-induced contact dermatitis, if poison sumac rash covers more than 20% of your body surface area or is located on the face, hands, feet, or genitals, contact a healthcare provider.
If someone exposed to poison sumac has a severe allergic reaction that causes facial swelling, difficulty swallowing, or trouble breathing, go to the emergency room immediately or call 911.
Are There Complications of a Poison Sumac Rash?
Skin infection is the most common complication of poison sumac rash. Scratching itchy skin can create open sores or wounds vulnerable to bacteria. Contact a healthcare provider if you have any signs of infection, such as:
- Fever and chills
- Pus (liquid puris) oozing from blisters
- Increased redness in rash areas
- Swelling
- Tenderness
- Warm-to-the-touch areas of skin
- Pain or burning sensations around the rash
Never Burn Poison Ivy, Oak, or Sumac
Every part of the poison sumac plant contains urushiol’s toxic compounds. Not only does urushiol cause skin rashes, it can also cause severe mucous membrane irritation and internal complications if a Toxicodendron plant is burned and the smoke is inhaled. Urushiol smoke exposure may lead to morbidity and, in rare cases, can even cause death.
Tips to Prevent a Poison Sumac Rash
The best way to prevent a poison sumac rash is to block urushiol oil from making skin contact. Wear long sleeves, long pants, boots, gloves, and a protective face mask like a gator to pull up over your chin.
Because urushiol can cling to clothing and shoes, take precautions not to transfer the oily substance to yourself or other items when undressing. Always wash footwear, clothing, and any tools or equipment exposed to urushiol thoroughly to prevent poison sumac rash.
Summary
Poison sumac can cause a red, itchy rash that often blisters. The rash itself isn’t contagious, but the invisible oil that causes the rash (urushiol) can cling to fabric, pet fur, or your skin. Any urushiol oil that isn’t properly washed off is like a contagion and spreads rash-causing allergens. Poison ivy, poison oak, and poison sumac all contain the same rash-inducing oil. However, the urushiol oil in poison sumac can cause a more severe allergic reaction.
