Poison Ivy Overview

 

 

Introduction

 

A

 resin is a chemical formed and secreted by plants or insects in order to gain a survival advantage.  Rhus genus plants (poison ivy, poison oak, poison sumac and other members) secrete urushiol (from urushi, Japanese for "lacquer"), a white, sticky, lipophilic (dissolves in fat) resin which leaks from the leaves, stems and other parts  when touched, turning brown in the air. Urushiol is toxic to plant eaters, sparing the leaves and berries.  

 

Rhus in Greek is sumac.  Sumac in French is tall. In the USA, 85% to 90 % of the population reacts on exposure to poison ivy resin with a brisk contact dermatitis-redness of the skin, blisters, and intense itching-usually 24 to 48 hours after the exposure, though brisk reactors may have signs of the rash within 6 to 8 hours.  

 

They all secrete urushiol, the individual plant sends the urushiol up to all its surfaces, where it intersperses itself between outer layer cells.  Touching any such part is like tapping a trigger, and the adherent resin attaches itself to the cloth or hair or skin of any creature brushing by.  The toxin can stay fully active on dead plant parts for 5 years or more, and burning the plant material in a given fashion sends the resin up in smoke which can affect sensitive persons.

 

 

An Experiment

 

In the 1990's, military personnel were tested to see if a dermal protection system (DPS) would be useful in various chemical warfare situations.  The investigators chose to expose the subjects to urushiol, since its high level of penetration would simulate other toxins.  Patches smeared with urushiol were applied to area with DPS and areas not protected. 

 

The intensity of the "poison ivy" on the DPS shielded skin was 2 points less than that seen on unprotected skin (scale = 0-5 points, in 0.5 unit increments).  Hence the chance that the DPS was no better than the penetration of unprotected skin was less than 0.001 or 1/1000.  It is impressive that urushiol established some penetration of the DPS, and the investigators planned other testing before accepting the effectiveness of the DPS.  ^[2]

 

 

Pathophysiology

 

How does the urushiol work?  In a healthy "sensitive" person, with normal adult immunity 85% to 90% of the US adult population, the urushiol attaches to skin cell protein as a hapten (German haptein "to fasten or touch"), which causes immunoregulatory cells in the body recognize the protein-urushiol complex as foreign matter, and attack it, with all the vengeance had it been a splinter!  Killer T-lymphocytes are called in and start blasting away at the outer skin cells inappropriatedly ID'd as "nonself."  

 

This reaction progresses to contact dermatitis.  It requires intact T-cell immunity, so babies and infants and HIV T-cell depleted or other immunosuppresed individuals, such as post- kidney transplant and others on immunosuppressive therapy, chemotherapy, lymphoma patients, and others do not develop contact dermatitis on contact with uroshiol resin.

 

 

 

Prevention

 

Protection:  Recommendation #1:  If you are one of the 10% to 15% of the population who has not yet reacted to poison ivy, assume you will-first, people who haven't reacted yet just haven't been exposed enough times to urushiol; also, you won't know when you've transmorphed to reactivity until you have a breakout.  Prevention-avoidance, skin protection-clothing, gloves, footwear, hat, face and eye protection-all are helpful.

 

Recommendation #2:  When working around grass and weeds and plants, cover most areas, and shower immediately after exposure using Fels soap on potentially exposed areas. 

 

Recommendation #3:  your dog may bring it in on his coat, burning wood on the patio chimney or elsewhere may carry urushiol in the smoke-contact of smoke bearing the resin or breathing it in can be problematic.

What happens if you eat poison ivy, oak, sumac or other Rhus leaves or stems or berries or roots and you are a reactor?  Get real, who is going to do that?!  Unless you like stomatitis, glossitis, and esophagitis, don't do it!

 

 

The Rash of Poison Ivy

 

It itches and burns and is red and affects exposed places intensely, but don't be surprised if you find it in places where sweat soaked through a shirt or hat or waistline, which allowed a "short circuit" which drew the urushiol through the fabric to your skin-ditto for resin laden smoke.

First, think when you contacted the ivy or oak, etc. 

 

 

Topical, Home Rx

 

If you haven't had many showers with Ivory soap, get a bar of Fels Naptha soap and cleanse each patch or area carefully.  This soap contains Stoddard's or White's solution (petroleum distillates) which were originally formulated to help dry cleaners get stains out without dissolving the fabric back in the 1920's.  Today this soap (found at various grocery markets and drug stores) is used in laundry to get out stains and for poison ivy home care. 

 

How does it work?  Remember the description of urushiol-very sticky, used to make lacquer, binds to skin cells as a hapten.  The chemicals in Fels Naptha soap actually dissolve the urushiol resin, thereby ending the cell-destructive process initiated by contact with the plant. 

 

Topical steroids (Cortaid OTC), antihistamine/calamine lotions (Caladryl, which have antipruritic and drying properties), epsom salt soaks, topical antibiotics (Bacitracin ointment for secondary bacterial infection-be sure to see your doctor right away for signs of infection.

 

 

 

Some Immunology

 

 

"Poison Ivy Shots"-many decades ago a "vaccine" was given to prevent poison ivy contact dermatitis.   Today these "shots" have become a depo-medrol injections or other long-acting steroid injections, which come with all the side-effects of systemic steroid therapy, particularly if given long term.

 

IgE-mediated allergies, like ragweed, grass and other pollen allergic rhinitides, are humoral, not cellular.  Allergists attack them in many ways, including immune-hyposensitiztion, also called immunotherapy and, by some, "allergy shots." 

 

 

Specific, Targeted Therapy

 

Contact poison ivy dermatitis results from self-attack on urushiol-primed skin tissue by lymphocytes is cell-mediated.  A short burst of prednisone-say 5 to 10 days, tapering off as indicated, as prescribed by your doctor will take care of those angry T-cell lymphocytes nicely and you will be on the mend quite promptly.  The way steroids such as Cortaid and prednisone reduce the lymphocyte attack, in fact is that they cause lysis (cell rupture) of lymphocytes.

 

Soothing self care:  Aveeno oatmeal tepid baths-not too hot;  Epsom salt soaks-2 tbsp. per 2 quarts H₂O or 1 cup in 6-8in. lukewarm tub water. 

 

Family history?  With such a high prevalence of "reactivity" to poison ivy, and the fact that recurrent exposure increases the likelihood of future reaction, it's best to assume you are a reactor and take precautions, even though it is said that as you grow older, your risk decreases, which has some truth in it, since human T-cell population and immunity declines with advancing age.

 

Remember: "Leaves of three, don't touch me!"

 

References

[1] The World Book Encyclopedia 1989: P pp.-603-604

[2] Vidmar DA; Iwane MK. "Assessment of the ability of the topical skin protectant (TSP) to protect against contact dermatitis to urushiol (Rhus) antigen."  Am J Contact Dermat.  1999; 10(4):190-7 Department of Military and Emergency Medicine and Dermatology, Uniformed Services University, Bethesda, MD 20814-4799, USA.

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Notes: [1] The World Book Encyclopedia 1989: P pp.-603-604 [2] Vidmar DA; Iwane MK. "Assessment of the ability of the topical skin protectant (TSP) to protect against contact dermatitis to urushiol (Rhus) antigen." Am J Contact Dermat. 1999; 10(4):190-7 Dep

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