Drugstore.com, the nation's No. 1 online pharmacy, has seen aspirin sales increase about 15%, more than would be expected in recent months, although it's too early to draw conclusions about why that's happening. But doctors and pharmacists say more people are asking about pain alternatives and should remember that aspirin carries dangers, too.

"My guess is that if aspirin was launched in 2004, it would not be an over-the-counter drug," says pharmacist Harold DeMonaco, senior editor for Harvard Health Publications. "People have the misunderstanding that if you can simply buy it without a prescription, that it is completely safe to use. But every drug has side effects."

More than 100 billion aspirin tablets are consumed worldwide each year, says the Aspirin Foundation. The more-than-100-year-old drug is commonly used to treat pain and inflammation associated with headaches, toothaches, minor arthritis and muscle or soft tissue injuries. It is also often recommended in small doses for people at high risk of heart attack because it helps prevent blood clots.

But aspirin also is believed to help cause gastrointestinal bleeding and stomach irritation. It has been around so long it never went through the stringent tests today's drugs do to become non-prescription drugs, DeMonaco says.

Chronic pain sufferers need to be the most wary, says rheumatologist Michael Stevens of San Mateo, Calif. Aspirin is fine for the occasional headache or minor pain, he says. Plus, it's cheap: 120 tablets cost less than $7 recently on Drugstore.com. But Stevens doesn't recommend it for chronic pain suffers, because they'd have to take so much of it, potentially increasing their risks.

For a long time, aspirin was the only pain reliever available without a prescription. Then others came along, including ibuprofen and naproxen, sold in non-prescription form as Advil and Aleve, respectively.

Even Aleve has been linked to heart risk in one recent study. DeMonaco says that study needs to "be taken with a large grain of salt," as it contradicts others. Stevens says he's more likely to switch patients who cannot use COX-2s to other anti-inflammatory drugs such as Aleve or ibuprofen than to aspirin.

Pharmacologist Steven Weisman, a paid scientific adviser to Bayer, says consumers and doctors who shunned aspirin for newer medications may try it as the risks of newer medications become more known.

"We may see a little bit of the turning of the tide," Weisman says. "They will look back to what they trusted in the past."