There are many plants in the world that can cause poisoning in a person. More times that not, this poisoning is a dermal poisoning. One of the most common of the plant poisons is that of poison oak. Poison oak contains a substance known as urushiol. "Urushiol is a general term applied to the toxic substance in the sap causing allergic contact dermatitis in people. It is actually a mixture of phenolic compounds called catechols, potent benzene ring compounds with a long side - chain of 15 to 17 carbon atoms. The side chain may be saturated or unsaturated with one, two, or three double bonds" (Dawson, 1954, 1956). The immune reaction and specificity of the catechol molecule is determined by the long side - chain and the poison oak catechol contains 17 carbon side - chains.
Urushiol is only found in resin canals. Some people are so sensitive that two micrograms or less than one millionth of an ounce can severally effect them. It is insoluble in water and is difficult to wash off the skin. It is like tar because it sticks to the body. It penetrates the epidermal layer where it binds to proteins of deeper skin membranes. When it is bound to cell membranes, urushiol is virtually impossible to wash off. When it attaches itself to cell membranes, they attract T - cells that try to get rid of them. A cell called the Langerhan's cell can become bound to the urushiol. The Langerhan's cell is a branched white blood cell. It goes to nearby lymph nodes where replicas of the white blood cells are programmed to recognize the urushiol. These white blood cells then try to eliminate the urushiol. This process is the natural immunity to the poison urushiol in poison oak and in other plants.
Creams and lotions are the most effective way to relieve the pain and/or itching. Urushiols can become soluble in mixtures of soap, lotions, and oils and therefore can spread further and grow worse. A product known as Tecnu Oak-n-Ivy Cleanser can be found in some medical magazines. "It contains a mixture of organic solvents and wood pulp by-products which remove terpene resins and urushiol from the skin" (Daphne). Other organic solvents like alcohol may remove the urushiol residue.
