Poison ivy and poison oak plants contain an oil called urushiol. Urushiol, found not only in the leaves of the plant but also in the stems and roots, results in an allergic reaction and produces an itchy rash. Itching, redness and blisters may appear 12 to 72 hours after the initial contact with the oil.
Contact With Urushiol
Urushiol is found in all parts of the plants, even when the plants are dead. The oil is absorbed quickly into the skin. It also can be inhaled if the poison plants are burned. Urushiol is easily transferred from one object to another, so clothing or tools that touch the plants, or pets that rub against them, can pick up the plant oil and pass it to a person. The first time urushiol touches the skin, an allergic reaction seldom occurs. With repeated exposure, sensitivity to urushiol develops.
Identification
According to the American Academy of Dermatology, the saying “Leaves of three, beware of me,” can help identify poison ivy and oak, but a more accurate saying is “Leaflets of three, beware of me.” Each leaf on poison ivy and poison oak has three smaller leaflets. The middle leaflet has a longer stalk than the two on the sides.
Poison Ivy Rash
The poison ivy rash may appear as itchy skin where the plant touched your skin, with red streaks or general redness where the plant brushed against your skin. Hives, which look like small bumps or larger raised areas, will appear. Blisters filled with fluid may develop and the fluid may leak out.
Poison Oak Rash
Poison oak rash is similar to the skin reaction seen with poison ivy. This is because it is triggered by the same substance: urushiol. The rash causes intense itching in both of poison ivy and poison oak.
Misconceptions
The rash is not contagious. You cannot catch or spread a rash after it appears, even if you touch it or the blister fluid, because the urushiol will already be absorbed or washed off the skin. The rash may seem to be spreading, but either it is still developing from earlier contact or you have touched something that still has urushiol on it.
Considerations
The rash from poison ivy or poison oak can be severe and become infected. If you notice the blisters are oozing pus or develop a fever greater than 100 F (37.8 C) or if the rash does not get better within a few weeks, consult a physician.
References
- American Journal Nursing; Emergency: Treating Poison Ivy, Oak and Sumac; Daniel Boelman; 2010
- Nursing; Poison Ivy: Patient Education Series; Lippincott Williams & Wilkins; 2008
- UpToDate: Patient Information: Poison Ivy
