Poison oak lore: What holds up and what doesn't

In Placer County, poison oak is a plant almost everyone knows, either by sight or by rash. Long before settlers arrived, the Nisenan Maidu Indians here learned how to live with it. They carefully observed plants and shared that knowledge over generations. Some of this knowledge still makes sense today while other parts are stories not supported by science. Here's a look at four ideas from lore about poison oak and what research says about each. 1. Wash quickly to reduce the rash Many cultures have advised washing soon after touching poison oak. Science supports this. The oil in poison oak that causes the rash is called urushiol. It sticks to skin and clothing very quickly. Research shows urushiol begins to bind to skin proteins in about one minute. Washing soon after exposure can remove some of the oil before it causes a reaction. Washing does not always prevent a rash, but it can reduce how severe it becomes. It remains the most effective step after possible contact. Takeaway: Rinse exposed skin with soap and cool water right away. A dish soap that cuts oil and lifts it much like axle grease is good to use, too. 2. Know the plant to avoid it Traditional plant knowledge included recognizing poison oak in all seasons. This remains good advice today. Research agrees that knowing what poison oak looks like helps people avoid contact. The best-known clue is the "leaves of three" pattern. Poison oak can grow as a shrub or a vine. Its leaves may be green or red, depending on the season. In spring, it has whitish green flowers. From late summer into winter, it produces pale green or white berries. Because poison oak changes through the year, learning its many forms is important. Avoiding contact is the best way to prevent a rash. Takeaway: Learn the plant so you don't touch it. 3. Manzanita and other plants: Treat rash, but do not immunize Some traditional stories say plants growing near poison oak, including manzanita Arctostaphylos manzanita, were used to reduce its effects. You may hear claims that Native people drank manzanita tea or ate the berries to "immunize" themselves. Science supports only part of this idea. Manzanita contains astringent compounds that can help dry irritated, wet skin. This makes it reasonable as a topical treatment for rashes. However, there is no research showing that eating the berries or drinking tea made from the leaves prevents a poison oak rash. Other plants appear in plant lore as well. California mugwort Artemisia douglasiana has many traditional uses, but there is no strong evidence that it prevents poison oak rash. Jewelweed Impatiens capensis, a folk remedy popular on the East Coast for reducing poison ivy rash, is sometimes crushed and applied to the skin. It can grow in damp, wooded areas of Placer County. Studies show mixed or weak support for jewelweed helping an existing rash and no evidence that it prevents one. Takeaway: No food or plant has been shown to safely make a person immune to urushiol. Manzanita may soothe irritated skin when used externally, but eating or drinking it will not prevent a rash. Jewelweed may offer limited relief. Prompt washing is the best response. 4. 'Tolerance' from small doses? Not safe at home Another belief is that repeated small exposure to poison oak can train the body to react less. Scientists do know that, in medical settings, the immune system can sometimes be trained to respond differently to allergens. There is also a belief that drinking milk from goats that eat poison oak can make people immune. Goats can break down urushiol in their digestive systems. This does not mean their milk provides protection to humans. Poison oak reactions are unpredictable. For some people, reactions become worse with repeated contact. Because responses vary, doctors do not recommend trying to build tolerance at home. There is no safe, proven method outside medical research. Takeaway: Don't expose yourself on purpose. Respecting tradition, using evidence The plant knowledge of the Maidu is based on long observation. Some of it matches modern science: avoid contact, wash quickly, and treat irritation safely. Other parts are not supported as safe practices today. Understanding where tradition and science meet helps us stay safer outdoors. When in doubt, follow guidance from plant experts, including UC Agriculture and Natural Resources, and enjoy the outdoors without the itch.