What poison oak looks like
Poison oak in western states
What poison sumac looks like
Poison sumac drawing
Because it is caused by contact with the leaves or stems of the poison ivy plant (fresh or dry), the distribution of the rash is usually linear where the plant brushed along the skin. The rash itself is red and often contains vesicles. The fluid in the vesicles is just edema and cannot spread the rash further. The idea that the rash is contagious and can be spread by touching the involved areas comes from the fact that not the entire extent of the rash appears at one time. It can take up to 2-3 weeks for all of the rash to appear. Usually the rash appears within 12-72 hours of contact with the plant and may last several weeks.
Linear papules and vesicles of poison ivy (Rhus) dermatitis
Poison ivy dermatitis
Poison ivy rash
Blisters from a urushiol-induced dermatitis
Urushiol induces an allergic reaction (type IV hypersensitivity reaction) which involves a response by T lymphocytes, a type of white blood cell. In fact, the first exposure to urushiol may not result in a rash at all. What the first exposure does is prime the immune system to respond to the allergen on next encounter. When the reaction does happen, the body produces memory T cells, which remember the allergen and induce a faster and more extensive rash the next time the allergen is encountered. This happens with every exposure to the plant oil.
Steps to take If there is contact with poison ivy:
If you develop a serious rash, you need to see the doctor right away. Serious rashes include swelling around the eyes, mouth or genital areas or a widespread eruption. These eruptions need to be treated with systemic medications. You should see your doctor immediately if the blisters are oozing pus or you have a fever.
Hot water may make the itching better for an instant but because it allows for more circulation into the affected area, may make the rash actually worse.
If the exposure was extensive, a prescription strength cortisone gel or even oral prednisone may be necessary. Prednisone treatment must continue for 12-14 days as premature termination of treatment may result in a flare of the rash.
Post-steroid flare of poison ivy rash (Rhus dermatitis)
It’s important to remember that the plant oil does stay on tools and gloves used in gardening, so handle those with care. Clothing, shoes and gardening tools used during exposure to poison ivy need to be washed to assure removal of the plant oil. The oil can also be brought into the house by pets that go outside as it stays on the fur.
Do not burn poison ivy plants. The oil of the poison ivy plants can be aerosolized by burning the plant. The aerosolized particles in the smoke can coat the skin and cause a severe, widespread reaction. Inhaling smoke from burning poison ivy plants can cause severe irritation or injury to your eyes and breathing passages.
Prevention is the name of the game with poison ivy!
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