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  • Writer's pictureLatifat Apatira, MD MPH

Poison Oak is beautiful. Just don’t touch it.

One of the things I’ve learned about people going out into nature for the first time is fear. Fear of being out of one’s comfort zone. Fear of getting hurt from things like mountain lions and coyotes and rattle snakes and ticks and poison oak and getting lost. It would be unfair for me to tell those of you who may be in this camp that you have absolutely nothing to worry about because these dangers do exist. However, the extent of these dangers are likely not as all-encompassing as some might think. Especially if you know what to look out for. And to put the fear to scale, I’ve been hiking the trails of the bay area for most of my life—I’ve never seen a rattle snake; I’ve seen a mountain lion once from afar; I’ve seen several coyotes, but they seemed more afraid of me than the other way around, and I’ve never gotten a tick bite or poison oak.

Today, we focus on poison oak. Know what it looks like, don’t touch it and let it be one less fear in nature.

Photos by Latifat Apatira (unless noted otherwise)

Poison Oak

Poison oak, Toxicodendron diversilobum, is a shrub-like vine that grows all over the bay area. It crawls over fences, trees, crowds trails and has been very successful at establishing itself as a dominant plant force in most of the opens spaces we humans like to explore. It’s also deciduous, meaning that the leaves of poison oak changes color in the late summer and fall from fresh green to brilliant shades of yellow, orange and red, before it looses it’s leaves altogether.

San Mateo, CA. Poison oak is one of the few native plants that give us west coasters a taste of New England Autumn.

But these are not the reasons we know about poison oak.

American Academy of Dermatology

This is.

(Photo: American Academy of Dermatology,

Yup, the unsuspecting human who’s arm brushes against the plant will obtain, within 12 to 72 hours, the “gift” of a very uncomfortable, hot, itchy, painful, rash complete with swelling and blisters.

The rash-inducing gift from poison oak is due to a compound called urushiol, a natural oil contained in it’s leaves, stems and roots. The rash won’t kill you, but might make you miserable for awhile.

So, it’s best to avoid it. If you don’t know how to recognize poison oak, your only option is to never touch any plant at all while outdoors. That’s no fun! Being outside is all about engaging all the senses – seeing, smelling, touching, hearing, and yes, if your knowledgeable enough, tasting.

So let’s recognize it.

There are a few rhymes out there to help people remember what to watch out for:

“Leaves of three, let it be.”

“Leaves of three, beware of me.”

First rule: Poison Oak leaves cluster in sets of three.

See how the leaves are in sets of three?

But don’t let this alone be your guide! Blackberry vines may also appear to have only three leaves. You'll unknowingly avoid awesome and tasty wild blackberries that grow in much of the same places that poison oak do. Don’t miss out on yummy berries by avoiding all plants with leaves of three. You need another rule.

Second rule: Poison Oak vines don’t have thorns. Blackberry vines do.

Blackberry on the left, poison oak on the right. Look closely at the blackberry stem.

Let these two major rules be your guide.

Also note that blackberry leaves are serrated, like a saw’s jagged edge. Poison oak leaves may be lobbed or notched but they are not serrated.

If you do get poison oak, it’ll be alright (remember, I’m a doctor!). Wash the contacted area with soap and water as soon as possible, as well as any item that might have contacted the plant. Try not to scratch the rash. There are many over the counter topical creams and lotions as well as allergy medications that might help. The rash isn’t contagious and for most people, it resolves after a few weeks. However, if you have a serious reaction, it’s always a good idea to go see your doctor.

And there you have it. One less fear. Know how to identify poison oak, simply avoid it, marvel at it's beauty (and power) and enjoy your hike!

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