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If you spend time outdoors, you have probably met poison ivy, poison oak or poison sumac. Most people are sensitive to the oily sap — its active ingredient is urushiol — found in the roots, stems, leaves and fruit of these plants. On the skin it causes an itchy, blistering rash: first itching, then a red rash, then blisters, appearing anywhere from a few hours to several days after contact.
How bad the rash gets depends on how much sap touches the skin and how sensitive you are. Burning the plants is dangerous too: soot coated with the sap can get into the eyes, nose, throat and lungs.
Recognising the plants
| Plant | Where and how it grows | Leaves | Flowers and fruit |
|---|---|---|---|
| Poison ivy | throughout the United States except Alaska, Hawaii and parts of the West Coast; a vine or small shrub, trailing on the ground or climbing low plants, trees and poles | three glossy leaflets, smooth or toothed; reddish in spring, green in summer, yellow, orange or red in autumn | may have greenish-white flowers and whitish-yellow berries |
| Poison oak | a low shrub in the eastern and southern United States; tall clumps or long vines on the Pacific Coast | fuzzy green leaflets in threes, lobed or deeply toothed with rounded tips | may have yellow-white berries |
| Poison sumac | a tall shrub or small tree in bogs and swamps in the Northeast, Midwest and parts of the Southeast | clusters of seven to 13 smooth-edged leaflets; orange in spring, green in summer, yellow, orange or red in autumn | may have yellow-green flowers and whitish-green fruit in loose clusters |
The rash is not contagious
The rash cannot pass from person to person, and scratching does not spread it over the body — it appears only where the oil touched the skin. It can seem to spread when it appears over time, because the oil is absorbed at different rates on different parts of the body, or because of fresh contact with oil on clothing, pets, tools or under the fingernails. The oil can stay on almost any surface, sometimes for years, until washed off with water or rubbing alcohol. The fluid in broken blisters is not plant oil and does not spread the rash.
Preventing it
- Learn what the plants look like, and stay away from them.
- If you may be working near them, wear long sleeves, long trousers tucked into boots, and impermeable gloves; wash garden tools and gloves regularly.
- Wash a pet that may have brushed against the plants, with pet shampoo and water while wearing rubber gloves. Most pets are not sensitive, but the oil on their fur can give a rash to whoever strokes them.
- If you touch a plant, wash your skin with soap and cool water, and wash your clothes, as soon as possible — the sooner, the better the chance of removing the oil.
Treating the rash
The rash, blisters and itch usually go away in several weeks without treatment. Do not scratch the blisters: bacteria from under the fingernails can infect them. To relieve the itch:
- wet compresses, or soaking in cool water;
- over-the-counter corticosteroid creams, or prescription corticosteroid tablets;
- over-the-counter skin protectants — zinc acetate, zinc carbonate, zinc oxide and calamine dry oozing blisters; baking soda or colloidal oatmeal ease minor irritation and itching; aluminium acetate is an astringent that relieves the rash.
A pharmacist can advise on over-the-counter medicines.
See a doctor if
- your temperature is over 100 °F;
- the rash has pus, soft yellow scabs or tenderness;
- the itching worsens or keeps you awake at night;
- the rash reaches your eyes, mouth or genital area, or covers more than a quarter of your skin;
- it is not improving within a few weeks, or is widespread and severe;
- you have difficulty breathing.
Sources
- MedlinePlus, U.S. National Library of Medicine, "Poison Ivy, Oak and Sumac," drawing on the National Park Service. https://medlineplus.gov/poisonivyoakandsumac.html
- U.S. Food and Drug Administration, "Outsmarting Poison Ivy and Other Poisonous Plants." https://www.fda.gov/consumers/consumer-updates/outsmarting-poison-ivy-and-other-poisonous-plants
- Rewritten in hubnx's own words.
Licenza: CC0 1.0 (pubblico dominio) · Tratto da medlineplus.gov
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