Cortisone (prednisone) works, which is what Frank suggested. You can fine it in creams in several products to relieve itching. However, it's palliative, like everything else mentioned above, each of which I have found to be effective to some degree. The buckhorn is good for mosquito bites, to and the Touch-me-Not impatiens is good for a brush with nettles. The poison ivy active agent is urushiol, an oil. Best cure is prevention, but if exposed, an oily soap, or a solvent followed by liberally application of soap is good. Tecnu is a product that claims not only to dissolve the oil, but to chelate it, so it is neutralized. Tecnu works.