Charles W. Bryant,
HOW STUFF WORKS, Plants can be your best friend or worst enemy in a survival scenario. They can be a source of food and water, provide shade and shelter, or even come in handy as rudimentary clothing -- just ask Adam and Eve about their fig leaves. But eating the wrong plant can make you very sick, and even touching one can leave you with some gnarly skin issues. You won't die from touching the wrong plant, but a serious case of poison ivy without the relief of a remedy can hamper your chances of success in a survival scenario. And scratching the itch can lead to infection and bigger problems.
Itchy and Scratchy
Poison ivy, oak and sumac are the three most likely culprits in the wild. In the United States, especially in the mountains of the East and Pacific Northwest, these three green plants are found everywhere you turn. The old rule of thumb is easy to remember and will save you every time -- ""leaves three, leave it be."" If you see bright green leaves in groups of three, there's a good chance it will be either poison ivy or oak. Sumac shrubs and trees, which are 5 to 20 feet (1.5 to 6 meters) tall, have seven to 14 leaves per stem.
Other Itchy Plants
While ivy, oak and sumac are the most plentiful plants that can cause dermatitis, or skin irritation, you should also be on the lookout for boxwood leaves, century plants, ginkgo seeds, horse apple sap, oleander leaves, pawpaw fruit and trumpet creeper leaves. Do yourself a favor and either grab a book on the local flora or do some Internet research so you can identify offending plants when you travel.
If you mess up and you're suddenly covered in an annoying, itchy rash, fight the temptation to scratch for relief. Not only will this help spread the rash, but you could also develop an infection. If you know you've come into contact with one of these plants, wash the area that you touched immediately with soap and water, and you may be able to avoid the rash setting in. Make sure your first aid kit is stocked with some skin helpers. Calamine lotion and hydrocortisone cream are good to have on hand. They won't cure the rash, but they'll aid in the itch factor. Applying cool compresses or running cold river water over the rash may also help to thwart the itch.