What is poison ivy?
Poison ivy produces urushiol, an oily chemical that causes an itchy, painful reddish rash in people who come in contact with the plant.
Poison ivy (Toxicodendron spp.) is a plant native to North America. The ivy is a climbing vine related to the cashew family. Poison ivy produces an oily chemical (urushiol) onto the surface of its leaves. When people come in contact with poison ivy, the urushiol can cause an allergic skin reaction that produces reddish, itchy, and painful inflammation of the skin (dermatitis). Close relatives of poison ivy plants that produce similar dermatitis symptoms are poison oak and poison sumac. In addition, mangoes and Japanese lacquer trees also can produce urushiol.
Is poison ivy contagious?
The poison ivy rash is an allergic reaction to an oily chemical from the leaf surface. This is an individual's allergic response to the chemical and is therefore not considered to be contagious. However, if a person comes in contact with the oily chemical from an affected patient's skin or clothing, then the urushiol could be passed on and a poison ivy rash may develop in a second individual. Direct contact with the oily chemical causes the symptoms and signs attributed to poison ivy.
What is the incubation period for a poison ivy rash?
Dermatologists suggest that the first exposure to poison ivy has an incubation period of about five to 21 days before the rash appears. However, repeated exposure to poison ivy results in the rash appearing more quickly (about 12-48 hours). The diagnosis made with the patient's history and physical exam and usually requires no further tests. Consequently, the diagnosis is made by likely exposure to poison ivy and the appearance of the rash symptoms and signs described above.
Is it possible for a poison ivy rash to spread?
Poison ivy is not contagious and is not spread like an infectious disease from person to person. However, it can spread if the oily chemical on one person's skin is touched by another person. Even if the oil is on a person's skin or clothing, anyone who comes in contact with the irritant may develop symptoms. In addition, if the person who has poison ivy touches clothing or other areas of his body that has the irritant on the skin surface, they can spread the irritant to other parts of their own body. Consequently, it is very important to clean off the skin and clothing that has been exposed to the oil and to not scratch or touch the developing rash area if it has not been cleaned off as the person could transfer oil to the eyes, mouth, or other areas of the body. Showering with warm soapy water helps to remove the oil and can reduce the chance of any spread. Washing the exposed area within 20 minutes after exposure reduces the symptoms and signs of poison ivy rash.
Treatment of Poison Ivy Rash
The initial treatment for someone who has recently been exposed to any of these plants includes rinsing the affected area with copious amounts of warm water within 20-30 minutes of exposure to remove the oily plant resin. The effectiveness of rinsing decreases with the passage of time, as the oily plant resin is quickly absorbed into the skin. Some authorities recommend rinsing with rubbing alcohol, commercially available poisonous plant washes, or degreasing soaps and detergents.
How long does a poison ivy rash last?
Most individuals with poison ivy will have the rash and other symptoms and signs gradually resolve over a period of about one to three weeks. Dermatologists recommend immediately rinsing or showering the skin with lukewarm soapy water to remove the oily chemical responsible for the symptoms. This can reduce or eliminate the chance of spread to other areas of the body or to other individuals who may otherwise contact the irritant on an individual's skin. In addition, thoroughly washing clothing that may be exposed to the oily chemical is key to prevention of the spread of poison ivy. Once the oily irritant is removed, spread of the rash is prevented, although itching and some pain may take a few days to fade.
When should someone seek medical care for a poison ivy rash?
Individuals with a poison ivy rash usually do not require medical care and have the symptoms resolve in about one to three weeks. Home care may include cool showers, cool compresses, calamine lotion, and/or hydrocortisone cream. If any blisters develop, simply leave them alone and do not scratch the irritated skin area.
However some patients may be very sensitive or allergic to the oily chemical produced by poison ivy. If any of the following symptoms or signs develop after contacting the irritant produced by poison ivy, the individual should seek immediate medical care:
- Difficulty with breathing or trouble swallowing
- Swelling, especially around the eyes
- A rash develops on the face and/or genitalia.
- A rash covers most of an individual's body.
- Nothing relieves the discomfort (itching, pain) of the rash.
Allergies can best be described as:
Medically Reviewed on 7/30/2022
Goodman, Rhonda. "Allergic Contact Dermatitis: Poison Ivy." Medscape.com.
Pray, W. Steven. "Poison Ivy: The Classic Contact Dermatitis." US Pharmacist 32.3 (2007): 11-15. <https://www.medscape.com/viewarticle/557163>.
Stephanides, Steven L. "Toxicodendron Poisoning." Medscape. June 13, 2022. <http://emedicine.medscape.com/article/817671-overview#a6>.