Having grown up in California, learning how to identify poison oak was a must. And it’s a good thing I did as I’m hugely allergic and catch the rash really easily. Over the years, I’ve learned a lot about how to avoid this gnarly native plant and, when I fail, how to treat a poison oak rash.

For anyone who likes to spend time outside in California, this post is for you. You don’t have to be afraid of poison oak—there are steps you can take to avoid the plant and the rash if you do happen to come in contact. Enjoy worry-free time outside with these simple steps below.

In a hurry? Here’s what you need to know in just one minute:


Know your enemy

Poison oak, or toxicodendron diversilobum, is the West Coast cousin of poison ivy. The leaves of both plants are covered by an oil called urushiol, which causes a red, bumpy, itchy rash that takes at least ten days to recede.

Though a lucky few are immune, contact with poison oak can result in a range of reactions, from mild itching to severe, life-threatening systemic inflammation. The bottom line is that urushiol is nothing to mess with—the chemical is so tenacious that it has been found on Native American artifacts, still potent 1,000-plus years later.

An ounce of prevention is worth…not getting a rash

When it comes to avoiding a rash from poison oak, knowledge really is power and knowing what you’re looking for is half the battle. Depending on its size, this plant can look like a woody vine, thicket or shrub, or even just a bundle of sticks. It’s happiest in the shade near creeks, but can grow in a variety of climates. Hands down the best way to identify this plant (as with most plants) is by studying it leaves. You don’t need to be a botanist – just remember these simple rhymes:

Leaves of three, let it be

Poison Oak - POST
Poison oak is easiest to identify in the fall when its leaves turn a vibrant red. Just remember: “leaves of three, let it be” and “if it’s hairy, it’s a berry.” Photo: Judy Kramer

Poison oak leaves are almost always in groups of three and can vary from large, flat, matte and green, to small, sharp, shiny and reddish. While the color will vary throughout the year, the leaves always come in threes. Oh, and don’t think you’re home free if the stalk doesn’t have any leaves as even the stems of poison oak plants can cause the rash.

If it’s hairy, it’s a berry

Another helpful rhyme to add to your repertoire. Most of our native berry plants also come in leaves of three. However, the stems and leaves of berry plants have small thorns or hairs, while poison oak is smooth. Be careful, though! Poison oak often grows in and amongst berry bushes, so when in doubt, steer clear of both plants.

Cover up

Sometimes avoiding contact with poison oak just isn’t possible. It doesn’t take much—even just brushing up against the plant can spread the rash-causing oil. By keeping your skin covered, you lessen the risk of exposure. But here’s the key: urushiol oil can spread from clothing to skin and even from clothing to furniture to skin. If in doubt, grab a pair of gloves or event just use plastic bags to protect your hands when removing clothing that has potentially had contact with the plant. Take extra care to immediately wash hands and be vigilant by changing and washing your clothes in hot water (separated from uncontaminated clothing) after particularly close encounters.

Pro tip: keep your ankles and wrist covered. I tend to catch it there most frequently.

Don’t hug the dog (until after they have a bath)

For you dog lovers out there, this might come as very difficult news. Dogs are a great vector for the urushiol oil, which can easily be transferred from them to you. If you’re concerned your pooch is contaminated, give them a good soapy bath and then bathe yourself too (see below for more washing tips). Ticks are also a concern, which is yet another reason to wait for that hug…it’ll be worth it.


If you touch poison oak or think you were exposed to it, the first thing to do is wash the area thoroughly with soap as soon as you can, and try not to touch your face or other body parts in the meantime. If you have access to them, specialized products like Technu and Zanfel are great for removing urushiol and keeping the rash at bay. Next, wash your clothes and anything else that may have come in contact (car seats, backpacks, shoes) in hot water, separately from unaffected laundry.

Pro tip: think of urushiol like motor oil. You really have to work with lots of soap to get it all off.

Have a poison oak rash? Here’s what to do:

Do you want the good news or bad news first? Well, the good news is that the rash and itching will go away without treatment.  But the bad news is that it will likely take some time and it could be even be a couple weeks – or more.

I feel for you. Having had this rash too many times in my life, it’s just the worst. But there are a few things you can do to make yourself more comfortable. Here’s my regimen:

  • Netflix
  • Cold compress on the rash for 15-20 minutes throughout the day. This will help relieve some of the irritation.
  • More Netflix
  • Calamine lotion, topical antihistamine or hydrocortisone cream to reduce itching
  • Oral antihistamines like Benedryl (diphenhydramine) will also help reduce itching
  • Take a cool or tepid bath in a mixture of water and soothing baking soda
  • If it’s really bad, don’t delay, see your doctor. You may need something stronger like an oral or topical steroid to slow the rash’s aggressive march.

Is there any upside to poison oak?

Turns out that while it is a pest to humans, it makes great forage and habitat for wildlife. Poison oak is rich in phosphorous, sulfur and calcium, so the leaves and berries are a valuable food source for deer, birds and other wildlife. It also provides shelter for birds and small mammals and has been found to contribute to overall bird density and diversity in California. Good to know, right?

Stay safe out there and as always, happy trails!

About Post

Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 87,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

Scroll to top