All of these plants (ivy, oak and sumac) contain an oily resin called Urushiol (pronounced “you-ROO-shee-ol”) which causes the rash. Urushiol has as its dermatitis-producing principle, pentadecylacatechol. This chemical does not evaporate but dries quickly on clothing, shoes, animals and tools.
Urushiol remains potent for a year or longer. Therefore, it is important to wash any tools, shoes or clothing after exposure to poison ivy. The resin will remain active on these articles and can cause a rash months, or even years, later. Removal of the oil with an effective cleanser, such as Tecnu® is helpful to avoid contaminating unsuspecting victims in the future. Dish detergent instead of Tecnu® is a very suitable alternative if you have water available. The main thing you are trying to do is to remove the poison ivy oil from the skin. Alternately, many hashers use rubbing alcohol as a very good yet inexpensive poison ivy oil cutting agent.
It has been estimated that 70 percent of the population is susceptible to poison ivy. Dark-skinned individuals seem less susceptible than others. Elderly individuals and infants are not as susceptible to the resin but they can still get it. Children become susceptible by age 3 and are highly susceptible by age 12. You can develop the reaction at any time during your life. Sensitivity is just a matter of being exposed enough times until the body becomes allergic to the Urushiol [personal note: so the medical literature claims – I personally think they (medical community) are somewhat bullshit in this case – I think some people are more susceptible regardless the amount they have been exposed, but who am I to say, I’m not a doctor, I just try to play doctor…].
Those who are exposed usually pick up the resin on their legs and palms and then transfer it to other areas, often their face and genitals (so quit playing with yourself until you’ve washed your hands) – Seriously, after a few circle beers when you’re hitting the tree line to make room for more beer, you need to think about where your hands have been when you’ve been on trail – I think you get the idea. It only takes about 15 minutes for the resin to begin to bind with the keratin (top) layer of the skin, which then sets the inflammatory process into motion. It is noteworthy that a rash rarely breaks out on the palms, since the keratin layer of the skin is often too thick for the resin to bind there, but it can be spread from the palms to other parts of the body.
The best thing to do if you know you’ve been exposed to poison ivy/oak/sumac is to wash your skin as soon as possible with something that will cut the urushiol (rubbing alcohol, Tecnu®, detergent, etc), in which the resin is soluble. Beer or other beverages containing alcohol will help to dissolve the resin if rubbing alcohol is not available, but will have diminished impact. Soap works, but not as well. If the oil has been on the skin for less than six hours (although bonding can occur in as little as 10-15 minutes), a thorough cleansing with strong soap or oil cutting media, repeated several times, can lessen or even prevent a reaction.
If you do wash with soap or the like, be careful that you just don’t spread the urushiol from one place to another. Use a LOT of COLD water. Be aware that the water is simply spreading the oil around; the idea is to use enough water to wash all of the oil from your body.
Do not use hot water, which can open your pores to the oil.
The resin is can be absorbed quickly into the skin. If the oil is on your skin for as little as ten to fifteen minutes, it can lead to an allergic reaction. However, for many they have enough time to finish the hash and then deal with it (but if you know you get PI, try to remove it when you finish trail, don’t wait until after the circle or something, because it will probably be too late to prevent it.
If you do get poison, the eruption is characterized by redness, papules (bumps), vesicles (blisters) and linear (“in a line”) streaking. Mild cases can last 5 to 12 days. More severe cases can last up to 30 days or longer. The eruption usually appears within two or three days but may occur within as little as eight hours. The eruption rarely is delayed longer than ten days.
Once the rash appears, the original oil has all bonded to the victim’s skin, so it can’t be spread to others. Contrary to popular belief, the fluid in the vesicles or blisters is not contagious and will not spread the rash to other parts of your body nor any one else’s body. The blisters are the body’s natural allergic reaction to poison ivy. If the blisters break and ooze, the fluid does not contain the oils that cause spreading. The rash will frequently break out in stages and continue spreading for the first 1 or 2 days.
If new areas of rash appear after 3 days, you are probably getting re-exposed to the plant oils, most likely from contaminated clothing or shoes, tools, or even your dog that you had on trail (their fur protects them but can harbor the oil for a prolonged period of time). As mentioned above, the resin will remain on any exposed objects such as clothing or equipment for a lengthy time (unless it is cleaned). If you put on your exposed shoes a week later, you can wipe the resin from your shoes onto your face or other areas causing a possible case of PI.