Rash from Poisonous Plants

Childhood Skin Problems

Medically Reviewed by Brunilda Nazario, MD on March 19, 2021

Photo of poison ivy skin rash

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© Scott Camazine / Phototake -- All rights reserved.

Poison ivy, poison oak and poison sumac are plants that contain anirritating, oily sap called urushiol. Urushiol triggers an allergicreaction when it comes into contact with skin, resulting in an itchy rash,which can appear within hours of exposure or up to several days later. A personcan be exposed to urushiol directly or by touching objects -- such as gardeningtools, camping equipment and even a pet's fur -- that have come into contactwith the sap of one of the poison plants.

The rash that results from the poison plants is a form of allergic contactdermatitis. (Dermatitis is swelling and irritation of the skin.) Skin is notautomatically sensitive to urushiol. Sensitivity builds up after the skin isexposed to the substance. When initially exposed to urushiol, the skin alertsthe immune system of the presence of the irritating chemical. (Usually, novisible reaction will occur the first time a person comes in contact with apoison plant.) The immune system then prepares a defensive reaction for thenext time the skin encounters the substance. This sensitizes the skin so thatnew contact with urushiol causes an allergic reaction. Read moreabout poisonous plant allergies.

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Article: Allergies:Poison Plant Allergies: Poison Ivy, Oak, and Sumac
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Text: "Allergies: Poison Plant Allergies: Poison Ivy, Oak, and Sumac", WebMD Medical Reference provided in collaboration with the Cleveland Clinic

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