SUNDAY, June 15 (HealthDay News) -- It's rare these days to see a teenager without a cell phone in hand, texting for hours at a time, seemingly without health consequences. But, when older folks attempts to spend the day e-mailing, instant messaging and surfing the Web on a handheld device, repetitive stress injuries -- such as "Blackberry thumb" -- are much more likely to occur.

Dubbed "Blackberry thumb" because of the popularity of that particular model of wireless personal digital assistant (PDA), this repetitive stress injury occurs because these devices rely almost solely on the use of your thumbs for typing, instead of all your fingers.

Any device that relies on the thumbs for typing can cause this type of injury because the thumbs simply weren't designed for such use.

"Blackberries and other PDAs can cause tendonitis from working in such a small space with the thumbs," explained Kristen Crowe, a certified hand therapist with Beaumont Hospital in Royal Oak, Mich. "The problem is that people are doing the same activity for long periods of time that the body just wasn't meant to do. Teens seem to do OK with it. It's around age 40 or 50 the 'itises', [such as tendonitis], start to crop up."

Margot Miller, president of the American Physical Therapy Association's Occupational Health Special Interest Group, added: "Because the keyboard of the PDA is so small, and because the thumb, which is the least dexterous part of the hand, is overtaxed, the risk of injury just skyrockets."

"The use of PDAs is no longer limited to the eight hours spent in the workplace," Miller said. "More and more, people are depending on these devices to stay in touch with friends and family before and after the workday and on the weekends, as well as having access to work when they leave the office. That is where the heart of the problem lies." .

Symptoms of "Blackberry thumb" include pain and numbness in the thumbs and joints of the hand.

Most people who rely on PDAs wouldn't readily give them up, even for an injury, so it's fortunate that there are treatments available.

Crowe's first suggestion is to take a break from the device for just a little while. "If it's painful, switch your activity until you feel rested. Don't try to work through pain thinking it will go away. Take a vacation if you can," she recommended.

"Try to do more on your computer. Don't write phone books on your PDA. Limit yourself to 'yes' or 'no' answers when you can," advised Dr. Charles Leinberry Jr., a hand and wrist specialist at the Rothman Institute at Thomas Jefferson University Hospital.

Leinberry, who is also an assistant clinical professor of orthopedic surgery at Jefferson Medical College in Philadelphia, said that splinting, usually with a custom-made splint worn while you're sleeping, can relieve some of the pressure on your thumb and other joints, and improve your symptoms.

Both Crowe and Leinberry said it's important to pay attention to your workspace ergonomics to make sure you're not putting any extra stress on your thumb and hands. Crowe added that many times, small changes in the work area can have a big impact on your health.

"Getting a new office or doing more work at home -- possibly at the dining room table -- can throw off your posture," she said, which can result in muscle and nerve disorders like tendonitis or carpal tunnel syndrome.

Crowe also recommended icing the injured area. And, both experts suggested doing strengthening exercises once the pain subsides. Ask your physician or physical or occupational therapist to show you what to do.

In the worst cases, Leinberry said that cortisone shots or surgery can be helpful.

But, he also pointed out, most people never have a significant problem.

"Just use common sense. Be smart with your use -- shorten answers and just use the devices when you need to. And, if you feel discomfort, stop using it and get in to see a physician," he said.

More information

To learn more about preventing repetitive stress injuries to the hand, visit the Cleveland Clinic.