The Mysteries of Poison Ivy, Oak and Sumac Revealed

By Ruth Werner, LMP, NCTMB
June 29, 2009

The Mysteries of Poison Ivy, Oak and Sumac Revealed

By Ruth Werner, LMP, NCTMB
June 29, 2009

Dear Readers,

In the summer, many of us enjoy time outdoors in the woods, hiking in the mountains or working with clients who are doing the same. One of the consequences of that pastime is the possibility of a common allergic reaction to a chemical called urushiol. This is the irritant found in the sap of three major plant species that are members of the cashew family: Rhus radicans, Rhus diversiloba or Rhus vernix. In other words, the topic for this column is poison ivy, poison oak, and poison sumac.

A lot of contradictory and flatly incorrect information is circulated about these plants and the rashes they cause, so I decided to take this opportunity to clear up some common misconceptions. This is in attempt to keep massage therapists safe, and to provide information to give useful advice to our clients who are dealing with these allergic reactions.

Poison Ivy, Oak and Sumac: What are they?

Poison ivy, poison oak and poison sumac are plants that are found in various places throughout North America. They favor wooded and watery areas. They have one feature in common: the presence of a chemical called urushiol that is carried in the sap of the leaves. The old rhyme, "leaves of three, let it be" applies to poison ivy and poison oak, as leaflets often appear in groups of three. Poison sumac can have leaflets numbering five, seven or more. One mark that is sometimes observed on these plants is shiny black spots that look like spatters of tar. This is actually the urushiol on the surface of the leaves.

The leaves of these plants are incredibly delicate, and even very gently brushing against them can allow the transfer of a tiny amount of urushiol, which then binds to cells deep in the epidermis. Symptoms, which include an itchy rash with fluid-filled blisters, typically develop 12-72 hours after contact with the oil. Some areas of the skin appear to react more quickly than others, so the rash may continue to develop over a few days. Further, the person may inadvertently spread the irritant on him or herself before bathing. This can make it appear that the rash is spreading spontaneously from the original site of exposure.

About 85 percent of the population is allergic to urushiol, although some people are more sensitive than others. It may take several exposures to launch an immune system reaction. Some people also find that their sensitivity declines with age: older people appear to be somewhat more tolerant of urushiol exposure.

Interestingly, humans and some other primates appear to be the only species sensitive to urushiol. Birds consume the berries of these plants with great enthusiasm. This is why they are often found growing near trees and fences: the seeds are spread by birds. Deer eat these plants with no apparent ill effects. And dogs don't appear to develop a rash, although they can effectively and enthusiastically share the urushiol that is on their fur.

Is it contagious?

Poison ivy and its partners are contagious from person-to-person only between when a person is exposed to the sap, and the next time that person bathes. This means that if a client arrives for a massage just after a pleasant walk in the woods, she or he may have had some exposure but has not yet developed symptoms. Receiving a massage at this point could put both the client and the therapist at risk for a much more extensive exposure to urushiol than anyone expects.

One example I witnessed along this theme was at a hot spring resort. An enthusiastic hiker joyfully made use of a public hot tub, not realizing that she had been exposed to poison oak during her morning walk. The oily sap spread on the water, affecting other bathers, and one of them had a very extreme reaction that bordered on anaphylaxis.

A poison ivy rash may involve fluid-filled blisters, but the fluid does not spread the rash. Scratching or popping the blisters, however, may introduce the risk of a secondary bacterial infection: definitely not a benefit.

It is important to understand that the cause of the rash seen with exposure to these plants is the sap, and only the sap. If the urushiol has been removed, even if the rash persists, the risk of the affected person spreading or sharing the rash is likewise gone. However, the oil in urushiol is amazingly stable and can retain its potency for months or longer. Dead plants can carry active urushiol for up to five years. It can also cling to fabric or metal, including the lawn mower or weed whacker that was used last season, the work boots that have been in the shed all winter, and the gardening gloves that are still on the tool bench. Another indirect way to contact this allergen is when it is vaporized in the atmosphere. For this reason, it is important never to burn clippings of poison ivy or its cousins.

What to do?

How do we limit the effects of urushiol? This is the million-dollar question, and it yields a surprising variety of answers. The one thing that seems consistently clear in the literature is that no single intervention appears to work on every person.

Experts agree that when exposure to urushiol is suspected, the area should be cleaned as quickly as possible. If the oil can be dislodged within 30 minutes the rash appears to be less extreme. The open question is how that removal should take place. Some people recommend treating the area with a skin-friendly solvent like rubbing alcohol or witch hazel first (the very scent of witch hazel takes me back to my poison ivy-filled youth!), rinsing with cool water, and then bathing with warm water and soap. Others suggest rinsing with warm soapy water right away. Some products have been developed that claim to be specifically targeted to shield the skin from urushiol, or to be especially effective at dislodging the molecules from skin cells, but the research on their efficacy is inconsistent at best.

Once the rash has emerged, a variety of topical applications are soothing and effective at managing the itching and swelling: calamine lotion (another evocative scent and color!), oatmeal baths and cortisone creams are all well-accepted.


Obviously an active urushiol-caused rash is at least a local contraindication for massage, but not because the rash is contagious or will spread; simply because any compromised skin is a possible invitation for secondary infection, and who needs to bring more circulation to an itchy area anyway?

Clients who have been spending time in areas that put them at risk are well advised to bathe before receiving massage. Massage therapists can give good advice about how to avoid contact with these plants and how to minimize their irritating effects. It's almost enough to make you look forward to autumn, isn't it?

For next time: The floor is open, and I am waiting for suggestions. This is your column, so let me know: what's on your table? Until then, many thanks, and many blessings.


  1. "Outsmarting Poison Ivy and Its Cousins." FDA Consumer magazine, Sept. 1996 Issue. U.S. Food and Drug Administration.
  2. "Poison Ivy, Oak & Sumac." 2009 American Academy of Dermatology.
  3. Poison Ivy, Oak and Sumac Information Center. 1999 - 2009 by Jim Dunphy.