Health Information

Ask Dr. H - Can you still spread poison ivy even after you've washed?

Q: My doctor says that once you wash off poison ivy sap from the skin, you can't spread it. If that's right, then why is it that whenever I get poison ivy it seems to spread to other areas? -D.C., Philadelphia

A: The skin rash (dermatitis) that causes poison ivy is due to the chemical "urushiol" contained in the plant's sap. All parts of the plant, from the leaves to the roots, contain urushiol. 85-90% of people who come in contact with the sap will get a poison ivy rash. The sap containing urushiol can rapidly penetrate the skin within 10 minutes after contact. Washing your skin within 5-10 minutes with soap and water or even hydrogen peroxide may prevent the rash. The problem is that either we don't know we've brushed against a plant, or the sap is left behind on our clothes to cause a rash days later when we handle them while doing laundry. Urushiol is an oil, and will stick to almost anything - clothing, sports equipment, hiking gear, garden tools- even your dog's or cat's fur.

Once you've developed the rash, you can't spread it to other parts of the body or to another person. That's because once the sap is washed away, there's no more allergen around to cause a rash. Those blisters you see are your body's reaction to a foreign substance on the skin. Blister fluid does not contain any sap and therefore can't spread the rash. New lesions that appear a few days after the initial rash are just less sensitive skin areas or areas where there was less sap exposure - not a spreading of the rash.

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Q: I've been having numbness in my pinkie finger and ring finger of my right hand for a few months. I just saw an orthopedic surgeon who diagnosed me as having cubital tunnel syndrome. He said it was from talking too much on my cell phone. How is this different from carpal tunnel syndrome? - S.L., Queens, N.Y.

A: Cubital tunnel syndrome, sometimes referred to as "cell phone elbow", is similar to carpal tunnel syndrome in that both conditions involve compression or entrapment of a nerve in the arm. Cubital (Latin "cubitum" = elbow) tunnel syndrome occurs when the ulnar nerve, the one responsible for the "funny bone" sensation at the elbow, becomes irritated or compressed. When you're holding the phone against your ear with your elbow flexed, it puts the ulnar nerve under tension and stretches it a bit. That nerve supplies sensation to the 5th finger (pinkie) and the ring finger. It's an overuse condition from repeated tension on the nerve or pressure on the elbow. Reaching, pulling handles or lifting can cause it too.

Carpal tunnel syndrome occurs when the median nerve that passes through the carpal (wrist) bones becomes compressed, irritated and inflamed. It's also typically caused by overuse of the hand and wrist. Unlike cubital tunnel syndrome, the thumb, index and middle fingers are affected in carpal tunnel syndrome. In carpal tunnel syndrome, symptoms are often worse at night due to a tendency to sleep with a bent hand and wrist.

Treatment of cubital tunnel syndrome consists mainly of avoiding the aggravating factor through elbow rest, using a hands free phone headset, switching hands when on a corded phone, splinting the elbow at night, anti-inflammatory medication, use of an elbow pad to reduce further trauma and a steroid injection if indicated. Surgery to free up the compressed ulnar nerve is reserved for situations where all other treatments have failed.

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