Poison Oak Facts

Poison oak leaves consist of three leaflets, hence the saying "leaves of three, let it be". The leaflets vary in size, shape and color but generally resemble white (scrub) oak leaves. They are larger in the shade (up to six inches) than in the sun. Leaf margins are wavy and may have lobes. Typically a bright, shiny green early in the season, the leaves turn yellow and red in the fall. Poison oak has three main growth forms: as an upright shrub, as a ground-hugging shrub, and as a climbing, clinging vine.

Getting Rid of Poison Oak

Poison oak will re-sprout readily if mowed or cut In small areas with moist, loose soil, the roots can be grubbed out. But avoid grubbing in dry or rocky soil because the roots break easily and will re-sprout from root fragments.

Goats, sheep and other animals will browse poison oak but the plants will come back.

Herbicides that work on poison oak include glyphosate (Roundup, Accord, Glypro, etc) and triclopyr (Garlon). Glyphosate should be sprayed late in the season for best effectiveness – when the leaves are still green but the plants have fruited For early season applications use Triclopyr. Re peat applications will probably be necessary. Follow all label directions. You can spray the foliage or apply the chemical on freshly cut stems.

I’m starting to itch!

All parts of the plant—leaves, stems, roots, flowers, fruits—contain the poisonous oil, urushiol (say“oo-roo-she-all”).

Urushiol is the severe rash-causing substance that comes off the plants and gets on the skin.

Here’s what you are up against when dealing with urushiol: it is (1) amazingly potent, and (2) it stays active for years at a time.

Urushiol is like a resin. It binds with the proteins in the skin within about 10-15 minutes, at which point it becomes extremely difficult to remove.

Regular soap and water, at that point will not remove urushiol. Rather, it will typically spread around that rash-causing substance. It is common knowledge among academics studying urushiol that even the tiniest particle of urushiol on the skin can cause a severe reaction. According to biochemist, Robert Smith, the amount of urushiol that would fit on the tip of a needle is enough to give 100 people the rash.

Also, it not only contaminates a human’s skin when it comes in contact, it contaminates gear and clothing. That is why wild land firefighters have such a hard time with poison oak/ivy rash. When the plants are burned in the wild, countless numbers (literally billions) of particles of urushiol get into the smoke and are delivered to, and contaminate, firefighters and their gear.

Good News - A Window of Time

Most people don’t react to the urushiol immediately. Reaction time varies from 6 or 8 hours and up to 3 days before the rash occurs. The ultra sensitive may react sooner. Therefore, there is a window of opportunity when urushiol can be removed from the skin and a rash avoided, or, dramatically cut down on the severity.

Get it off! Removing the poison oak oil, especially while in the forest or fighting a fire

Editor’s note: This information from Tecnu Labs focuses on reducing problems associated with exposure to poison oak. It endorses Tecnu products, but has some good suggestions.

Removing Oil (Urushiol) from the Skin 

There are three options:

  • Soap and water - helpful only if you can get to soap and water within 10 minutes after exposure. Fels Naptha soap works well. Soap and water is only helpful on clothing if washed in a laundry machine.
  • Tecnu original - is a liquid skin cleanser that can be applied directly to skin or gear. According to OSU’s Mark Christensen, “Tecnu breaks the bond that the urushiol has with the skin. Tecnu can be used with or without water. Without water, apply Tecnu, rub it around fairly aggressively and wipe it off with a cloth or paper towel. In extreme situations, even scraping off the used Tecnu (and urushiol) with one’s hand can be helpful.
  • Tecnu Extreme - was developed in 2005 after direct input the field. Tecnu Extreme has micro-fine scrubbing beads and special surfactants to remove embedded urushiol from the skin and is the best choice if there is access to water. Tecnu Extreme can be used to prevent a rash, stop the itching or stop an existing rash from spreading. Use Tecnu Extreme within 8 hours after exposure to urushiol to avoid the rash. Using it at any point before the rash actually starts can be helpful. Be extra diligent when washing areas where skin creases (behind the knees, the bend at the elbow, fingers) because urushiol accumulates in these areas.

Decontaminating Tools

Use Original Tecnu applied full strength onto a cloth or directly onto the tool and wipe it down.

After two minutes rinse or wipe off with a clean towel. Other products available to remove resins from tools should work, too. (NOTE: If something has a porous, synthetic handle it may be compromised by Tecnu. Test a small area first, before coating the item.)

It is crucial to remove urushiol from fibers in clothing/gear

The contaminant can accumulate on fibers.

Removing urushiol from clothing/gear

Gear/clothing contaminated by urushiol is utterly detrimental because a person coming in contact with that gear/clothing will be recontaminated and can get the rash without even coming in contact with the plants. According to Dr. Christensen, “Tecnu’s emulsifying properties will remove the urushiol from fabric fibers in clothing and gear."

Removing urushiol from cuffs & rims of gloves

The wrist area is a prominent place for urushiol to accumulate—even when one is wearing gloves and a long sleeve shirt. Twice a day, if possible, completely saturate cuffs with Tecnu and massage the fabric. After 2 minutes rinse off the cuff or glove rim with water. Removal from the fabric is important especially before resting/sleeping so that the urushiol does not re-contaminate the interior wrist (tender skin that is especially receptive to the rash).

Urushiol is like a resin. Heat and perspiration work as a vehicle to transfer it. From gloves it will move to the hand & upper arm. Forearms & hands should be treated with Tecnu or Tecnu Extreme, as part of a regular regimen

Removing Urushiol from Shared Gear: Uniforms & Over Garments, etc.

Urushiol will be present on over-garments that have been exposed to poison oak/ivy. If it is not removed, a person coming in contact with the clothing at a later date can be contaminated. It is advised that a way be found to remove the urushiol at some point. Tecnu doesn’t currently have a product. Use a degreasing type detergent and hot water. Keep contaminated articles separate from other laundry.

Stop the Rash from Spreading

The original contamination of urushiol tends to spread all over the body by different means. The rash will break out in one area, then another, and so on. The severity and spreading of the rash can be lessened if Tecnu Extreme is used quickly to remove any remaining urushiol that is on the body. Treating as much skin as possible the moment it is noticed (best is a full body wash in a shower) can dramatically reduce the severity of the reaction and contain the rash before it becomes fully realized and debilitating. An untreated rash can take weeks to overcome.

Tecnu Extreme has an active ingredient to help with the itching and healing. Tecnu original is a cleanser and does not have this active ingredient. Although, if Tecnu Extreme is not available, original Tecnu may be helpful to remove urushiol after a rash appears.

Healing the Rash

Using a topical product for drying up rashes can help the healing process. Tecnu makes a product called Calagel. There are other products on the market. You may already have something you like or that an occupational nurse may recommend (i.e. Benadryl, etc.) Calagel is unusual in that it has an antiseptic and a skin protectant added to it.

Related Content from OSU Extension

Ask an Expert

Have a Question? Ask an Expert!

Ask an Expert is a way for you to get answers from the Oregon State University Extension Service. We have experts in family and health, community development, food and agriculture, coastal issues, forestry, programs for young people, and gardening.

Ask Us a Question