Your Health: Poison Oak
by Terry Hollenbeck, M.D.
Apr 04, 2013 | 1225 views | 0 0 comments | 6 6 recommendations | email to a friend | print

It’s that time of year again when I treat an increasing number of patients suffering from poison oak rash.

Having treated thousands of cases of poison oak in my career, I’d like to share with you what I’ve learned about this miserable affliction.

The poison oak plant, which is so prevalent in our locale, contains an oil in its sap called urushiol. This oil is found in all parts of the plant — leaves, stems and roots.

Even in extremely minute quantities — say, a billionth of a gram — it can cause a very severe allergic reaction in the skin. This usually occurs within 24 to 36 hours of exposure.

Roughly 85 percent of the population is susceptible to this rash, and a lucky 15 percent has a natural resistance to it. Unfortunately, I’m in the first group.

You can be exposed to the oil by direct contact with any part of the plant or by indirect contact with an object that has urushiol oil on it, such as your own hands, clothing or tools. There have been reported cases of the smoke from burning poison oak causing either a skin rash or a reaction in the lungs, although I have never seen this in any patient I’ve treated.

Once you make contact with the oil, you have only a matter of minutes to wash it off before it will bind to the skin and begin the allergic rash.

The best way to remove the oil from the skin is to rinse with lots of water and then wash with soap and water. Most any kind of soap will do. Also, wash any object that may have come in contact with the oil using soap and water, including the clothes you were wearing.

Don’t forget to do the same to your shoes, tools and pets. Urushiol oil can remain active on inanimate objects for more than a year.

There are a number of over-the-counter products, including Tecnu and Zanfel, that are sold to be used on the skin after exposure to poison oak to remove the oil. I have heard mixed reviews on their effectiveness. For now, I’ll stick with water and soap.

A poison oak rash will always eventually clear up on its own if one is willing to wait it out. And there are abundant home remedies to cure poison oak, none of which has been proven to be effective.

However, there is effective, proven and safe medical treatment for those who wish not to suffer for several weeks.

Your doctor may prescribe some form of a steroid cream that is stronger and much more effective than over-the-counter cortisone cream.

If the rash is more serious, and especially if it involves the face, systemic treatment may be necessary. This involves the use of cortisone pills called prednisone, which is my preferred treatment, or a steroid shot. Either of these treatments is safe and very effective for most patients.

Your doctor will help determine the best treatment for your particular condition.

The bottom line is that you should avoid contact with poison oak, wash your skin and clothing as soon as possible if you do come in contact with any part of the plant, and see your doctor for effective medical treatment.

- Terry Hollenbeck, M.D., is an urgent-care physician at Palo Alto Medical Foundation Santa Cruz in Scotts Valley. Readers can view his previous columns on his website,, or email him at Information in this column is not intended to replace advice from your own health care professional. For any medical concern, consult your own doctor.

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