Урушиолға аллергия тудыратын өсімдік және оның зияны

Species of plant

Toxicodendron radicans, commonly known as eastern poison ivy or poison ivy, is an allergenic flowering plant that occurs in Asia and eastern North America. The species is well known for causing urushiol induced contact dermatitis, an itchy, irritating, and sometimes painful rash, in most people who touch it. The rash is caused by urushiol, a clear liquid compound in the plant's sap. The species is variable in its appearance and habit, and despite its common name, it is not a true ivy (Hedera), but rather a member of the cashew and pistachio family (Anacardiaceae). T. radicans is commonly eaten by many animals and the seeds are consumed by birds, but poison ivy is most often thought of as an unwelcome weed. It is a different species from western poison ivy, T. rydbergii, which has similar effects.

T. radicans grows throughout much of North America, including the Canadian Maritime provinces, Quebec, Ontario, and all US states east of the Rocky Mountains, as well as in the mountainous areas of Mexico Poison ivy's growth and potency has already doubled since the 1960s, and it could double again once carbon dioxide levels reach 560 ppm.

The fruits are a favorite winter food of some birds and other animals, including wild turkeys. Seeds are spread mainly by animals and remain viable after passing through the digestive tract. Birds may spread the seeds by regurgitation.

Urushiol induced contact dermatitis is the allergic reaction caused by poison ivy. In extreme cases, a reaction can progress to anaphylaxis. Around 15 to 25 percent of people have no allergic reaction to urushiol, but most people have a greater reaction with repeated or more concentrated exposure. Typically, the rash from the urushiol oil lasts about five to twelve days, but in extreme cases, it can last a month or more. Over 350,000 people are affected by urushiol annually in the United States. The pentadecyl catechols of the oleoresin within the sap of poison ivy and related plants causes the allergic reaction; the plants produce a mixture of pentadecylcatechols, which collectively is called urushiol. After injury, the sap leaks to the surface of the plant where the urushiol becomes a blackish lacquer after contact with oxygen. Urushiol binds to the skin on contact, where it causes severe itching that develops into reddish inflammation or uncoloured bumps, and then blistering. These lesions may be treated with Calamine lotion, Burow's solution compresses, dedicated commercial poison ivy itch creams, or baths to relieve discomfort, though recent studies have shown some traditional medicines to be ineffective. Over the counter products to ease itching—or simply oatmeal baths and baking soda—are now recommended by dermatologists for the treatment of poison ivy. A plant based remedy cited to counter urushiol induced contact dermatitis is jewelweed, though jewelweed extracts had no positive effect in clinical studies. Others argue that prevention of lesions is easy if one practices effective washing, using plain soap, scrubbing with a washcloth, and rinsing three times within 2–8 hours of exposure. The oozing fluids released by scratching blisters do not spread the poison. The fluid in the blisters is produced by the body and it is not urushiol itself. If plant material with urushiol is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty. An urushiol rash usually develops within a week of exposure and can last 1–4 weeks, depending on severity and treatment. In rare cases, urushiol reactions may require hospitalization. Urushiol oil can remain active for several years, so handling dead leaves or vines can cause a reaction. In addition, oil transferred from the plant to other objects (such as pet fur) can cause the rash if it comes into contact with the skin. People who are sensitive to urushiol can also experience a similar rash from mangoes. Mangoes are in the same family (Anacardiaceae) as poison ivy; the sap of the mango tree and skin of mangoes has a chemical compound similar to urushiol. A related allergenic compound is present in the raw shells of cashews. Similar reactions have been reported occasionally from contact with the related Fragrant Sumac (Rhus aromatica) and Japanese lacquer tree. These other plants are also in the family Anacardiaceae.

Immediate washing with soap and cold water or rubbing alcohol may help prevent a reaction. During a reaction, Calamine lotion or diphenhydramine may help mitigate symptoms. Corticosteroids, either applied to the skin or taken by mouth, may be appropriate in extreme cases. An astringent containing aluminum acetate (such as Burow's solution) may also provide relief and soothe the uncomfortable symptoms of the rash.