POISON IVY, POISON OAK, and poison sumac come from a family of plants known as Toxidendrons, and the irritating substance is a toxin called urushiol, which is found in the leaves, stems, and roots. They cause the skin to turn red,  develop a rash, swell, and blister; all accompanied by an intense and persistent itching that can last for days. The inflammation and itching are an allergic reaction to the toxin, and, while some people are more sensitive than others, almost everybody gets the reaction after exposure. You don't get poison ivy or poison oak just by standing close to the plant: You must touch it. Touching objects that were         exposed to the toxic sap, such as unwashed gardening tools or boots, can also pick up poison ivy. Dogs and cats, while not themselves allergic to poison plants, can brush up against them and get the sap on their fur, exposing people who come in contact with them, (Washing your pet, using rubber gloves, can free him of the toxin.) In addition, if these plants are burned, the toxin is released in the air and can be inhaled with the smoke, causing extreme irritation to the lungs.
The best cure for poison ivy is avoiding it in the first place. Both poison ivy and poison oak have leaves that grow in clusters of three, and both plants, as well as poison sumac, bear white berries in the summertime. Gardeners should wear gloves and boots to protect them from poison ivy.
There is a product that creates a barrier between your skin and the poison. It's called Ivy Shield and you can get it at some gardening and outdoor equipment stores. It won't completely protect you, but

it's a good beginning if you know you're likely to be exposed.
If you do get some sap on your skin, wash within fifteen minutes, if possible, with plenty of water, being careful not to spread the toxin to other areas of the body. Brown laundry soap is best. A poison ivy and oak cleanser called Tecnu is very effective in removing the toxin. It's an over-the-counter lotion. You just apply the lotion to the affected areas and then wash it off in a shower and towel dry. I've used it myself very successfully.
If you suspect that you've come in contact with the plants,      thoroughly wash your clothes with hot water and detergent. Even shoes and garden tools can harbor the poison so that wearing or using them at a later date can cause a reaction. I've had patients who have had cases of poison ivy that just wouldn't seem to go away, and it's usually because they continue to wear contaminated clothes or use contaminated tools.                                            If you do break out, try not to scratch, because you'll irritate the skin even more and possibly cause infection. However,     contrary to myth, scratching will not spread the poison ivy,        because the watery blisters don't contain toxin.
Home remedies for poison ivy rashes and itching include calamine lotion, baking soda, or over-the-counter cortisone creams. Calamine lotion helps coot the burning itch and dries up the blisters. Baking soda can be mixed with witch hazel to form a paste and then applied to the rash. Some people find that