The first published records of poison ivy in North America date back to the 1600.s. The term .poison ivy. was first used by Captain John Smith in 1609.

The poison ivy, oak, and sumac plants are among the most common allergies in the U.S., affecting upwards of 90 percent of all of the people exposed to them. The allergic agent in these plants is a substance called urushiol oil. The more frequently you are exposed to urushiol, the more likely it is that you will break out with an allergic rash. For the first time sufferer, it generally takes longer for the rash to show up [generally 7 to 10 days]. Poison ivy, oak, and sumac are most dangerous in spring and summer. When sap is plentiful, the urushiol content is high and the plants are easily bruised.

Learning to recognize these plants is the first step to avoiding an allergic reaction. Poison ivy, oak, and sumac plants producing urushiol belong to the family anacardiaceae. Most belong to the genus Toxicodendron (T), with several species known in the U.S.

Poison Ivy T. radicans and T. rydbergii: Each leaf is made of three leaflets, the one in the middle being larger than the others. The plant is primarily found east of the Rocky Mountains. In the eastern, mid-western, and southern parts of the country, poison ivy often grows as a vine, running along the ground or up a tree or fence. In the far northern Great Lakes and western areas, it can grow as a shrub. The leaves are red in the spring and turn green in summer. Poison ivy is the most widespread of the three types of poisonous plants.

Poison Oak T. toxicarium and T. diversilobum: Each leaf has three oak-like leaflets. This plant is most prevalent in the West, where it grows as either a low or a high shrub. In the eastern U.S., it is a low shrub. In the fall, the leaves turn yellow and then red.

Poison Sumac T. vernix   Symptoms:

After one comes in contact with urushiol, a rash will develop within 48 hours. However, because sensitivity to the allergen develops with exposure, first time contact may take up to 10 days to cause a rash. Any area of the body can develop the rash, though the rash is more likely in areas where the skin is thin, such as the face. The sap will be absorbed more slowly by skin that is thick, such as skin found on the forearms and legs.

Affected areas will initially itch and then become red, swollen, and blistered. It is commonly believed that scratching the rash causes it to spread. The rash is not contagious. You cannot catch or spread a rash once it appears, even if you touch the rash or the blister fluid. The rash may seem to be spreading but, it is either still developing from earlier contact or you have touched something that still has urushiol on it. The rash will persist, usually, for about 10 days.

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