Skip to content
My WebMD Sign In, Sign Up

Skin Problems & Treatments Health Center

Image Collection:

Childhood Skin Problems

Photo of poison ivy skin rash

Rash from Poisonous Plants

back buttonnext button

© Scott Camazine / Phototake -- All rights reserved.

Poison ivy, poison oak and poison sumac are plants that contain an irritating, oily sap called urushiol. Urushiol triggers an allergic reaction 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 person can be exposed to urushiol directly or by touching objects -- such as gardening tools, camping equipment and even a pet's fur -- that have come into contact with the sap of one of the poison plants.

The rash that results from the poison plants is a form of allergic contact dermatitis. (Dermatitis is swelling and irritation of the skin.) Skin is not automatically sensitive to urushiol. Sensitivity builds up after the skin is exposed to the substance. When initially exposed to urushiol, the skin alerts the immune system of the presence of the irritating chemical. (Usually, no visible reaction will occur the first time a person comes in contact with a poison plant.) The immune system then prepares a defensive reaction for the next time the skin encounters the substance. This sensitizes the skin so that new contact with urushiol causes an allergic reaction. Read more about poisonous plant allergies.

Reviewed on September 15, 2009

Today on WebMD

chafing
Pictures and symptoms of the red, scaly rash.
woman with dyed dark hair
What it says about your health.
 
woman with cleaning products
Top causes of the itch that rashes.
atopic dermatitus
Identify and treat common skin problems.
 
itchy skin
Article
shingles rash on skin
Article
 
woman with skin tag
Quiz
Woman washing face
Video
 

Itching for Relief?

Get Help With the

Loading ...

Sending your email...

This feature is temporarily unavailable. Please try again later.

Thanks!

Now check your email account on your mobile phone to download your new app.

woman washing her hair in sink
Video
close up of womans bare neck
Tools
 
Feet
Slideshow
woman with face cream
Quiz