January 28, 2011 Lawrence Jaeger is an expert Medical Dermatologist and discusses Progressive Pigmentary Purpura and treatments for Poison Ivy. There are several types of pigmented purpura, also called capillaritis, but the most common condition appears as pinhead-sized, reddish brown spots sprinkled in clusters on the skin, usually on the legs. The condition can fade away in a few weeks or months, or it can last years. To date, there is no effective treatment for pigmented purpura. The cause (etiology) of pigmented purpura is generally unknown. There may be tiny blood vessel (capillary) fragility that allows red blood cells to escape into the skin. These eruptions can occur in young as well as older adults. Onset has been noted as a side effect of certain medication, as a reaction to certain foods, or due to a viral infection. “Leaves of three – let it be!” aptly describes this woody vine with 2-4″ leaflets in groups of three. The center leaf has a longer stem than the other two. Poison ivy clings to tree trunks and other vertical surfaces with hair-like aerial rootlets that grow out of the stem. If a climbing surface isn’t available, poison ivy will grow as a free standing shrub. The leaves of poison ivy turn shades of red and purple in fall. Poison ivy is caused by an allergic reaction (allergic contact dermatitis) to the oily coating that covers of these plants. The resinous coating is called “urushiol”. These are called Rhus plants after the old scientific name (it was changed to toxidendron). A person doesn’t have to come in direct contact with the leaves, roots, or branches of Rhus plants to get the rash. One can get it from contaminated clothing. Even in winter the leafless stems and vines can cause the familiar skin rash. No one is born with sensitivity to Poison ivy, but if exposed enough most people become sensitized at some time and remain allergic. A sensitivity can change at any time. There’s no way to desensitize people allergic to Rhus plants. Dogs and other animals are not affected by poison ivy, but people can get the rash by petting a dog that’s been exposed. The rash itself is not contagious, and the fluid in the blisters does not spread the rash.