Poison oak
The skin reaction is a delayed allergy type reaction to oil (called urushiol) found on posion oak, poison ivy, and posion sumac. In the Wilamette Valley we have predominately poison oak. The oil is very potent such that exposure to 100 nanograms is enough to cause a skin reaction in most people. There are differences between people in how sensitive they are to the oil. Once the oil is washed and there is no more contact with the oil (including clothing, shoes) than the rash cannot spread. It seems to spread because areas that had larger oil exposure break out first (often within hours) and areas with least amount of oil break out later (up to several days later). Scroll down for pictures of the poison oak plant.- Localized redness, swelling and weeping blisters
- Eruption on exposed body surfaces usually
- Shaped like streaks or lines but may be in patches
- Very itchy
- Onset 1-7 days after the patient was in a forest or field
Poison oak rash on the armpit of a child
Poison oak rash on the arm of a child
Poison oak rash on the face of a child
See Immediately
- If the patient is experiencing difficulty breathing or swallowing
See in office in 1-2 days
- The caretaker is not sure if the diagnosis is correct.
- Home therapy is not working after 3 days.
- Facial swelling is present.
- The child has experienced severe reactions in the past.
- Signs of secondary infection are present like pus, diffuse redness around the patches or fever.
- Severe itching that precludes sleep.
Home Care Advice
Wash clothing that patient was wearing when in contact with the poison oak. The oil will remain active up to 2 weeks after contact with the plant. Pets can carry the oil on their fur also.Always shower with a soap when the rash first starts to erupt to remove any residual oil. Remind them to shower within 4-6 hours after contact with the plant in the future and to wash all their clothing that they were wearing that day.
Make up a solution with 1 tablespoon or more of baking soda in a cup of water and apply this to the area every 2 hours to promote drying and peeling of the skin.
Also try applying straight bleach to the area with a rag twice daily. The patient should use a test patch first to test for discomfort or extreme redness with this approach. If the bleach is too strong then they can dilute the bleach in half with water and add 1 tablespoon of baking soda to the solution to neutralize the acid in the bleach.
Soaking in the tub or swimming pool as often as possible to hasten drying and peeling will help also.
To help control the itching, Benadryl, 1 mg/kg/dose, can be given every 6 hours.
Cut the fingernails short.
The rash is not contagious. The oil has variable penetration times and therefore one sees a variable period of eruption.
If the rash lasts longer than 2 weeks, becomes infected or the child is getting worse, then the child should be seen.
Remind the caretaker and child to recognize poison oak. “Leaves of three, let it be” The poison oak sap or oil, urushiol, is present in the leaves, stems and roots of the plants. This oil is present all year long but is worse when the plant is in full bloom. The plant produces berries in the summer and turns a beautiful red color in the fall.Pictures of poison oak plant
