Summertime itch

What you need to know about poison ivy, sumac and oak

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Winnipeg Health Region
Wave, Summer 2014

What are poison ivy, sumac and oak?

"Poisoning" from plants such as poison ivy, poison sumac and poison oak is an allergic reaction that happens when your skin touches oils from these plants.

The oily substance is called urushiol. Contact with the oil from these plants causes most people to have a rash, blisters and itching. This contact usually happens in the spring and summer. 

Poison ivy can be found throughout Manitoba. Poison oak is not common in Canada and is mostly found in southern Manitoba. 

Poison ivy and poison oak have three leaflets on each stem and grow as a vine or bush. Poison ivy can grow as a vine twining on tree trunks or growing on the ground.

Poison oak mostly grows as a shrub. Common phrases to remember are: Leaves of three, let it be; Berries white, run in fright (although the berries on poison ivy really vary in colour from green to yellow). Poison sumac has opposing rows of seven to 13 leaflets on each stem, with one leaflet at the end of the stem, and has cream-coloured berries. It grows as a shrub or tree usually in damp, cool, marshy places. The poisonous oil, urushiol, is in the sap of these plants and oozes from any cut or crushed part of the plant, including the roots, stems, and leaves. Poison sumac is found in Ontario and Quebec.

How does the allergic reaction occur?

The allergic reaction happens after touching the oil from one of these plants. A reaction can also occur after contact with anything that carries the oil from the plants, including clothes, tools, animal fur, or ashes and smoke from burning plants.

What are the symptoms?

The symptoms of an allergic reaction to poison ivy, sumac, or oak include the following, from least serious to most serious:

  • Itching, often intense
  • Red blotches that may be raised or flat blisters that may show up in rows
  • Fever
  • Headache
  • Swelling of your throat and eyes
  • Overall swelling of your body
  • General feeling of discomfort - stomach cramps, nausea, vomiting, diarrhea
  • Sudden wheezing from breathing burning poison ivy (this can become a severe asthma attack)

Usually, the rash is first noticed one to two days after contact. How bad the rash will be depends on the thickness of your skin, how allergic you are to the plant, and how much contact you had with the plant's oil. The skin irritation normally disappears in seven to 15 days, although more severe cases may take longer.  

How is it diagnosed?

Your health-care provider will ask about where you have been recently and will examine the rash.

How is it treated?

To treat contact with poison ivy, sumac  or oak, follow these steps:

  • As soon as possible, wash all exposed skin with strong soap and water (or just water) to remove the plant's oils. This is most important as the oil can remain active for months.
  • Remove your clothes and shoes. Wash your clothes in detergent and water. Clean shoes as well.
  • Apply cool compresses to the area(s) for 20 minutes, four to six times daily to help relieve itching and provide a topical anesthetic. Then put calamine lotion or ointment on your skin to reduce the redness, ease the itching, and help dry up the blisters. Soaking in a lukewarm bath with baking soda (1/2 cup) or colloidal oatmeal added may help ease the itching. DO NOT put lotion containing antihistamine on your skin. Cover any oozing blisters with a clean gauze bandage soaked in a baking soda and water solution.

Once the oil is washed off the skin, the rash cannot be spread by scratching itchy skin or from oozing blisters. The blister fluid does not contain the urushiol so it does not spread the inflammation, although it is a common misbelief. However, scratching may lead to infection of the open sores. Taking an oral antihistamine, such as Benadryl, can help the itching but does not clear up the rash.

If the rash spreads to your face, mouth, eyes, or genitals, or if you have a fever, headache, extreme redness, pus, or other severe symptoms, see your health-care provider. He or she will recommend one or more of the following:

  • •Putting a corticosteroid ointment or cream on the affected areas two to three times a day, gradually reducing to once a day.
  • Taking oral corticosteroids such as prednisone.
  • Taking oral antibiotics or using an antibiotic cream if the rash becomes infected.

Because these are all potent drugs, ask your health-care provider about any possible side-effects or interactions with other drugs you may be taking.

How long will the effects last?

The rash usually takes one to three weeks to heal.

How can I take care of myself?

Follow the steps outlined above to treat your rash. In addition, keep the affected skin clean and dry. Keep your fingernails well-trimmed and clean. Try not to scratch your skin to avoid an infection. See your health-care provider if you develop severe symptoms. See your provider right away, or get emergency care, if your throat starts to swell, or your wheezing is getting worse.

What can I do to help prevent a reaction to poison ivy, sumac, or oak?

  • •Know what the plants look like and where they grow so you can avoid them.
  • Wear long-sleeved shirts and long pants if you are going to be in an area where these plants grow.
  • As soon as possible, preferably within five to 10 minutes of contact with the plant, rinse   exposed skin thoroughly with soap and water (or just water).
  • Be sure to clean under your fingernails.
  • Wash clothes in hot water and detergent to remove any oil that may be on them. Also clean shoes, tools, camping or fishing gear, or anything else that has been in contact with the plants.  Wear gloves when you do the washing and cleaning and then throw the gloves away.
  • Give any outdoor pets a bath if you think they have had contact with the plants. Wear gloves and avoid contact with your pet's fur while bathing them. Animals do not get a rash from poison ivy, but the oil can be carried on animal fur and transferred to humans.
  • Never burn poison ivy, oak or sumac. The oil can be carried by the smoke and if inhaled can cause a rash on the lining of the lungs, causing extreme pain and possibly fatal breathing problems.
  • Dead poison ivy plants can still cause a reaction. The oil can stay active for up to five years on any surface.       

Audra Kolesar is a registered nurse and Manager with Health Links - Info Santé, the Winnipeg Health Region's telephone health information service.

The information for this column is provided by Health Links - Info Santé. It is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a health-care professional. You can access health information from a registered nurse 24 hours a day, seven days a week by calling Health Links - Info Santé. Call 204-788-8200 or toll-free 1-888-315-9257.

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