You may notice however that a typical berry plant with edible berries will grow on plants with leaves of three. To make matters more confusing, sometimes poison oak has five leaves. There are however a few characteristics of poison oak and poison ivy that separate them from the plants that grow edible berries. Firstly, most berries grow with the protection of thorns—poison oak does not. And depending on the season, poison oak and and poison ivy will have a shine to their red or green leaves. Also keep in mind that not all berries are edible.
We suggest that you therefore leave wild berries for wild animals and eat only the berries bought in a food store.
Unlike an edible berry plant, poison oak produces a resinous sap in its stems, roots, leaves and flowers. The resin contains urushiol, which is the allergen that makes poison oak an undesirable plant to hike through.
If you do hike through poison oak without knowing, the affects on your skin will not be immediate.
Once you discover your unlucky contact with the plant you can wash the contaminated areas but most bath soaps have little effect on removing the resinous sap. In fact, the mild soap combined with the rubbing may spread the urushiol and increase the rash. Sometimes a little bit of rubbing alcohol can remove the urushiol residue from your skin.
However, if it has already penetrated your outer skin and bonded to the deeper skin cells it's just too late.
There are a number of lotions that can prevent the urushiol from touching the skin. This is a preventative measure for accidental contact. Otherwise, a little bit of Calamine lotion will help relieve the mild case of itching.
(The image on the left is poison oak.)