poison ivy, oak, or sumac can cause a rash (allergic
contact dermatitis ). The rash is caused by contact with the oil (urushiol) in
these plants. Urushiol is an
allergen, so the rash is actually an
allergic reaction to the oil in these plants.
immune system protects the body from viruses and
bacteria by producing
antibodies to fight them. In an allergic reaction, the
immune system overreacts and starts fighting essentially harmless substances as
though these substances were trying to attack the body. This overreaction
causes problems that affect the skin, nose, lungs, digestive organs, and blood
vessels. In the case of contact with poison ivy, oak, or sumac, it results in a
You are not allergic to these plants until contact with
urushiol triggers a reaction. The contact with urushiol can either be direct or
indirect, such as through clothes, tools, or other
Most poison ivy, oak, and sumac rashes develop within 8
to 48 hours after touching urushiol, but they can take as long as 15 days to
form.2, 1 The rash usually
takes more than a week to show up the first time you get urushiol on your skin.
But the rash develops much more quickly (in 1 to 2 days) after later
contacts. The rash usually lasts 10 days to 3 weeks, but more severe cases
can last up to 6 weeks.1 After the rash heals, there
are usually no permanent scars on the skin.
The rash is not
contagious. You cannot catch or spread the rash after it appears, even if you
touch it or the blister fluid, because the urushiol will already be absorbed
into or washed off the skin. Sometimes people mistakenly believe that the rash
is spreading because it appears later on different parts of the body. But the
rash only appears where urushiol has come in contact with the skin. So either
the rash is still developing from earlier contact, or you have touched something
that still has urushiol on it.
sensitive you are to poison ivy, oak, or sumac and how bad your reaction is depend primarily on your age and on the extent of the
first contact or first few contacts with the plant. Other influences include
physical activity and immune system function. Some
studies show that how allergic you are to the plants may be inherited.1
Complications from a poison ivy,
oak, or sumac rash usually do not occur in healthy people.
- The rash can occur all over the body
(generalized eruption) in highly allergic people.
scratching of the rash may discolor the skin or cause a bacterial
- The rash may come back or get worse if treatment ends
too soon or if the medicine used is not strong enough.
- In rare
cases, kidney problems (nephrotic syndrome) can occur. This can
happen in any severe allergic reaction and is not specific to poison ivy, oak,