Americans are bypassing their doctors and taking their rashes, earaches and other minor ailments to walk-in clinics in CVS, Walgreens and Wal-Mart stores. Quick Vote What will you do with your income tax refund? Spend it

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NEW YORK (CNNMoney.com) -- Americans, frustrated by endless waits at the doctor's office, are sidestepping their family physician and taking their rashes, strep throat and pink eye to stores such as Wal-Mart and Walgreens instead.

As this trend gains more traction, experts say it could define the market for primary care.

"In many ways these retail clinics are a response to a broken health care system," said Jonathan Weiner, professor of health policy and management at the Johns Hopkins Bloomberg School of Public Health.

"Not everyone has good access to primary care. We're also dealing with a shortage of primary care doctors in this country," he said.

Public health experts say retail clinics can, to some extent, fill the gap. But there's one caveat.

"I suspect these store clinics will be around for a long time, but they won't take over everything that a doctor can do," said Dr. Sherry Glied, chairwoman of the Mailman School Department of Health Policy and Management at Columbia University's School of Public Health.

Wal-Mart (WMT, Fortune 500), Walgreens (WAG, Fortune 500), CVS (CVS, Fortune 500) and Rite-Aid (RAD, Fortune 500) are among an expanding number of retailers that operate in-store health clinics.

It's not merely a public service. Bruce Carlson, publisher with health care market research firm Kalorama Information says retail clinics are a lucrative niche market for merchants.

The firm said these clinics numbered just over 1,200 in 2008 with annual revenue of $545 million. By 2013, Carlson said the total is estimated to reach 2,400 with revenue of about $2 billion.

These "retail clinics" are typically staffed by nurse practitioners. They administer vaccinations and treat customers - both uninsured and insured - for minor ailments. They also test for conditions such as hypertension and diabetes.

Although in-store clinics have only been around for a few years, it's only recently that their appeal has grown with consumers, according to the latest industry survey from consulting firm WSL Strategic Retail.

The survey, which polled 1,500 consumers, showed awareness about retail clinics has jumped to 56% in 2009, up from 38% in 2007.

The survey also showed that usage of store clinics has increased the most among younger consumers, who are less likely to have ties to a family physician or to have insurance.

Another group - consumers making $100,000 or more per year - are warming up to retail clinics faster than low-income or uninsured consumers who may not be able to afford the average $60 fee.

Candace Corlett, principal and retail analyst with consulting firm WSL Strategic Retail, said the overall appeal of retail clinics is the convenience they offer.

"Suppose I have a sore throat and I don't have time to go to the doctor, but I still have to buy my groceries," said Corlett. "I can stop at Walgreens after work, pick up my milk, and have my throat checked at the same time."

Health care as a commodity

Corlett believes the survey findings indicate consumers are treating health care as a commodity.

"Just like you pick your favorite store to get your beauty advice and products, people are picking their favorite store to get their earache treated," she said.

"There's a cultural shift that's going on with how we approach health care, and I think the retail market is ready for health care becoming a commodity," Corlett said.

No. 1 drug store chain CVS already operates more than 500 MinuteClinics at its stores nationwide. Rival Walgreens plans to expand its health and wellness clinics to more than 800 in-store locations by the end of the year.

Recently, Walgreens announced it would offer free care until the end of the year to people who are unemployed and uninsured.

"This is Walgreens being opportunistic. What a great way to get people to develop a new habit of using retail clinics," said Corlett.

Wal-Mart, the largest retailer, opened its first "limited scope" walk-in clinic in 2005 and currently operates more than 70 clinics in its stores.

Even supermarkets such as Safeway (SWY, Fortune 500) and Kroger (KR, Fortune 500) are staffing nurse practitioners in a few stores.

Will store clinics replace doctors?

In addition to offering a no longer than 15 to 20 minute wait and comparatively low cost versus a doctor's office, Johns Hopkins' Weiner said price transparency is another big selling point of store clinics.

Weiner said price transparency has become increasingly important as employers try to control their health care costs by offering workers tax-free savings vehicles such as health savings accounts (HSA) or health reimbursement arrangements (HRA).

These options typically lower premiums but raise deductibles before the insurance coverage sets in. The clinics allow consumers to keep better track of their account balances.

"Store clinics clearly advertise their prices, but most doctors don't," Weiner said. "This could be a competitive threat for doctors."

Still, both Weiner and Glied said store clinics are unlikely to fully replace doctors anytime soon.

"Right now people are using them for four things. Colds, sore throats, earaches and flu shots," Weiner said. "When it's something more serious than this, most people want to go to a doctor."

"No one really believes that retail clinics should be the model for health care," he said.

However, if store clinics eventually collaborate with other sources such as HMOs and hospitals, and expand services to deal with more urgent care, it could shake up the primary care market, Weiner said.

"The way they exist today, they are ideal for busy moms and adults with colds," said Weiner.