Health Education

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What is poison ivy?

Three plants are grouped together for the purpose of this discussion-poison ivy, oak, and sumac. Unless otherwise specified, the term “poison ivy” is used in reference to all 3 of these plants.

The “poison” is actually a chemical found in the sap called urushiol. Urushiol is in the leaves, stems, roots, flowers, and berries. It is a clear yellow color until exposed to air, which causes it to turn black. Therefore, it is advisable to avoid any leaves or plants with black spots on them, as there is a good chance that urushiol is present. Release of urushiol occurs in a variety of ways, such as by stepping on the plant, brushing past it, digging near the stem or roots, having an animal walk by or having it blown by strong winds.

The urushiol penetrates quickly and combines with skin proteins. The immune system then mounts an immune response to these foreign proteins resulting in inflammation (redness and swelling), itching, and blistering. Symptoms usually appear 24-72 hours after exposure, but this varies. Depending on the amount of sap, area of contact on the body, and sensitivity level of the person, symptoms may appear 6 hours to 2 weeks after exposure.

What does poison ivy look like?

The poison ivy rash starts with redness and itching and then progresses to red bumps and blisters (vesicles), with varying amounts of swelling. Segments of the rash are often referred to as linear, meaning the bumps are in lines. Although a linear pattern is the most common presentation of poison ivy, it can show up in patches or even in the shape of a handprint from the hand that came in contact with the plant. The face and genitals can get very red and swollen.

How does poison ivy spread?

Contrary to popular opinion, poison ivy rashes can only be caused by the sap itself. Neither the rash nor the fluid in the blisters can spread the poison ivy to other areas of the body. The rash is not contagious! Sap can linger on unwashed skin, under fingernails, on tools, pets, toys, and clothing. These are common causes of rashes that are frequently re-occurring or will not resolve.

Most typically, sap gets onto hands and under nails; it is then tracked all over the body by the hands. When you think of how often we touch our face, arms, neck, and so on, it is no wonder bumps eventually pop up in all sorts of places that could not have come in contact with the plant itself. The notion that the rash “spreads” is often related to the appearance of new patches over 2-14 days. Remember, depending on the amount and location of exposure, symptoms appear at different times.

What is the treatment for poison ivy?

If you are aware of the exposure at the time, wash the affected areas as quickly as possible. Plain water will help; the addition of soap or hydrogen peroxide may be even more beneficial. Unfortunately poison ivy sap penetrates and binds quickly, so this needs to be fairly soon after exposure. Once exposure is determined (even if not until rash appears), be sure to scrub under fingernails, wash clothes, and bathe pets if they were with you at the time.

Poison ivy cannot be cured, but the symptoms can be managed. With symptomatic care, mild cases will clear up in about 2 weeks. Topical steroids (prescription strength) are helpful if applied before the blisters appear, but once the blisters are present topical steroids are generally considered useless. Early application will hopefully decrease the severity of the reaction.

Topical treatments such as Calamine lotion or spray and colloidal oatmeal baths and lotions like Aveeno are helpful, along with cool compresses and soaks. Preparations containing aluminum acetate or alcohol can also be very soothing. Oral diphenhydramine (Benadryl) can be given to help reduce itching and assist in sleeping. Oral steroids, such as Prednisone, are reserved for only the most severe cases.

How can poison ivy be prevented?

There is a long-standing expression “Leaves of three, let them be.” This is excellent advice, but not all-encompassing! Poison ivy and oak can have up to 5 leaves, and poison sumac 7 to 13 leaves. Sometimes they are vines, other places they are found as shrubs. Appearances change in different regions of the country. You may want to take the kids to the Nature Center or similar facility for a lesson on recognizing poison ivy. Camp counselors should review the basics if the kids are hiking.

Be on the lookout for plants with black spots on the leaves or stems; remember the sap turns black when it is exposed to air.

Protective clothing can be helpful, but the sap can still soak through it. Vinyl gloves are necessary if you must move trees or shrubs entangled with poison ivy. The sap can penetrate both cloth and rubber gloves. A product called Ivy Block can be applied before situations with high risk of exposure. It forms a protective layer on the skin, which may help reduce the reaction to poison ivy. It is not a guarantee, and does not mean you do not have to still be careful, but many campers have found it useful.

Prevent additional contact with the sap by washing clothes that may have sap on them, scrubbing fingernails, and possibly even washing the dog if the fur may have picked up some sap.

Here are a few more tips or truths about poison ivy:

  • The rash is not contagious. The fluid in the blisters does not spread poison ivy. Only the sap itself can cause an allergic reaction.
  • The rash does not “spread”. Different areas break out at different rates, depending on amount of sap and the varying reactivity of the skin.
  • There is no “safe time” to handle poison ivy. The sap is hardy enough to endure most weather, and can cause a reaction even in the winter. Sap also remains active months after the plant dies.
  • Protective clothing is not enough. The sap can soak through clothes and both cloth and rubber gloves.
  • Apparent “immunity” is not a guarantee. People who seem to be immune to poison ivy may still react to it with a very high level exposure. Also, there is no evidence immunity can be obtained by eating foods such as cashews or mangos which are cross-reactive to poison ivy.
  • Herbal therapies need research. There is no evidence that substances such as jewelweed, feverfew, or plantain are beneficial in preventing or treating the poison ivy rash.