RIO DE JANEIRO - Brazil's well-heeled socialites swear by them. Legions of slum-dwellers from the country's hillside "favelas" don them almost every day. Minimum wage earners behind juice bar counters use them, as do newly minted millionaires and, alarmingly, construction workers.

In Brazil, literally everyone wears Havaianas, the now world-famous brand of rubber and plastic flip-flops that's celebrating its 50th birthday this year.

Since their 1962 introduction, Havaianas have joined soccer and samba as one of the great social equalizers in this country, among the world's most stratified societies.

Initially the workaday staples of the Brazilian poor, Havaianas have transcended both their modest origins and the country's borders to become an object of desire the world over, sold at Bloomingdale's and Neiman Marcus and coveted by Hollywood A-listers, European royals and suburban princesses from Seattle to Seoul.

Go ahead, put your best foot forward this summer with these expert tips on how to keep your feet healthy.

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  • Cut Down On Blisters

    A brand-spanking new pair of sandals often comes at the steep price of painful blisters. The sores form from the chafing that happens when a shoe rubs up against the skin until it balloons out and fills with fluid to cushion and protect the deeper layers of skin underneath, explains Jackie Sutera, a New York City podiatrist. <br><br> The first step for prevention, says Jane Andersen, a podiatrist in Chapel Hill, North Carolina, and a spokesperson for the <a href="http://apma.org/" target="_hplink">American Podiatric Medical Association</a>, is to buy shoes that are comfortable when you buy them and don't need to be "broken in." look for soft fabrics or leathers, and then take them for a test drive at home for an hour or so before you wear them outside to make sure they stay pain-free. You can also try lining any painful spots with moleskin to prevent the friction that ultimately causes blisters. <br><br> But sometimes even seemingly comfy shoes can cause problems. "I've purchased perfectly good pairs of shoes that have given me blisters," Andersen says. If you do end up in pain, clean the blister with regular hand soap and try to leave it intact. But if the pain is unbearable, use an alcohol-sterilized needle to poke a tiny hole in the side of the blister and drain the fluid out, leaving all the skin intact. Then apply some antibiotic ointment and cover with a band-aid. (Don't try this at home if you're diabetic, though, Andersen cautions.)

  • Prevent And Treat Dry, Cracked Heels

    Wearing open-backed shoes can spread the fat pad of the heel, causing the skin to crack, says Andersen. If you have any deep cracks where you can see dried blood, treat the heel with an antibiotic oil and cover with a band aid. <br><br> But if you just have run-of-the-mill dry summer heels, Sutera suggests treating them with an exfoliating moisturizer every day and run a pumice stone over them (only in one direction -- going back and forth can actually make the split skin worse) once or twice a week in the shower. <br><br> Dry cracked heels can also be a sign of a fungus, psoriasis, thyroid issues and diabetes, Sutera says -- if you're concerned, visit a podiatrist or dermatologist to get the all clear.

  • Rethink Your Flip Flops

    "Flip flop season is a busy season for me," Sutera jokes. "Especially toward the end of the summer when everyone's been walking around in these terrible shoes." <br><br> Over-wearing this summertime staple can cause stress fractures, heel pain and tendonitis, and can exacerbate hammertoes. "These are not shoes that we should be wearing from 8 in the morning to 8 at night," she says. "That's not really what these shoes are made for." <br><br> But that said, they're hard to resist. And there are ways you can make flip flops a safer footwear choice. <br><br> "Not all flip flops are created equally," she says. Look for a pair with a thicker sole with arch support -- and the more straps the better, as that can reduce stress placed on the toes to grip the flip flop so it doesn't fly off your foot. You shouldn't be able to bend the flip flop (or any shoe, for that matter), in half -- that's your first clue that it won't provide enough support. Reserve the ultra-thin ones for the locker room or pool.

  • Proceed Barefoot With Caution

    Walking barefoot might be one of the great joys of summer, but it can also put you at an increased risk of contracting viruses (think warts), fungus (like athlete's foot) or bacteria (which can cause a skin infection), Andersen explains. And these things tend to thrive in warm, moist environments, like a public pool. <br><br> Going shoeless also raises the risk of picking up foreign bodies, like stepping on glass or splinters. <br><br> Even walking around barefoot at home can be problematic, Andersen says, as you have no support on the foot. If your house has a no-shoes rule, consider throwing on a pair of supportive slippers or indoor flip flops.

  • Ease Sweaty Feet

    For some people, hot temps mean sweaty feet, and all that moisture can increase the risk picking up an infection. Andersen suggests wearing socks that wick excess moisture away, and changing out of damp socks as soon as possible -- if you can't shower, at least rinse your feet off. "Keep a nice, cool environment for your feet," she says. <br><br> One natural trick? Brew regular black tea, let it cool and tuck your feet in for 30 minutes -- Andersen says the tannins in the tea can decrease sweat production.

  • Get A Safe Pedicure

    For many, <a href="http://www.huffingtonpost.com/dr-robert-a-kornfeld/pedicures-and-toenail-fungus_b_946858.html" target="_hplink">polished toenails</a> are a summertime staple -- but some serious health risks might be lurking in the pedicure chair. <br><br> "Pedicures can be a source for real problems," Andersen says. Everything from the tools to that relaxing whirlpool soak can transmit nail fungus, wart viruses and sometimes serious bacterial infections. <br><br> To stay safe, consider bringing your own tool set, Sutera says, especially the foot file. (Clean your tools back home with a betadine solution.) She also tells her patients to avoid the "Wednesday Special," or a great deal that brings dozens more customers -- and germs -- through the salon. If possible, schedule your appointment at the beginning of the day, when technicians should be less tired and the tools and basins a little bit cleaner. <br><br> And don't shave or wax your legs for at least 24 hours before your appointment -- hair removal can cause microscopic cuts, increasing susceptibility to infection.

  • Watch Out For Germs

    One study from the University of Miami and the TODAY show found that a single pair of flip flops can harbor <a href="http://today.msnbc.msn.com/id/32453516/ns/today-today_health/t/can-your-flip-flops-kill-you/#.T78M0nlYv_g" target="_hplink">a whopping 18,000 bacteria</a>, including the dangerous superbug, Staphylococcus aureus. <br><br> Walking the streets in open shoes can mean kicking up all sorts of debris, including human vomit, feces, bird droppings and a whole host of other unappetizing things, Phillip Tierno, Ph.D., director of clinical microbiology and immunology at the NYU Langone Medical Center, told The Huffington Post. Then you take your shoes off and touch, say, your face. "It's a repository for everything you brought in from the outside and [you] don't give it a second thought," he said. <br><br> A few simple precautions can keep you safe: Tierno recommends removing your shoes before entering the house and avoiding wall-to-wall carpeting when possible, as it can harbor germs. So slip on a pair of slippers at the end of the day and wash your hands thoroughly -- between 25 and 30 seconds -- after you remove your shoes.

Not only have they become all but de rigeur in poolside Miami and beachfront Cancun, Havaianas now have a way of cropping up where you least expect them, from Paris' rarified haute couture catwalks to the red carpet at the Oscars.

The iconic flip-flops now rival uber-model Gisele Bundchen for the title of Brazil's most famous export. And though the word "havaianas" means Hawaiian in Portuguese, the flip-flops have come to be something of a symbol for Brazil itself.

"They're cool, colorful, laid back and chic," said Brazilian-born fashion consultant Abraao Ferreira. "They're the quintessence of everything that people find appealing about Brazil."

The numbers speak to that enduring popularity.

Last year, 210 million pairs of Havaianas were sold worldwide. Even with 15 per cent of total production exported to some 80 countries, enough of the sandals were sold in 2011 for nearly every man, woman and child in Brazil.

Legend has it that Havaianas' simple wishbone between-the-toe design was inspired by Japanese "zori" sandals, the traditional straw-bottomed footwear worn by geishas.

"It's true that some executives from (parent company) Alpargatas took a trip to Japan before the launch," in 1962, said Rui Porto, a longtime company executive who now works as a media consultant for the brand. "But the origins of this style of sandal date back to the dawn of time, to roughly the same era as the invention of the wheel.

"In fact, that's why there's no patent on them," Porto said.

Still, patent or not, Havaianas has kept the formula behind its squishy rubber soles a tightly guarded secret. Since most of its direct competitors make cheaper, plastic-soled flip-flops, Havaianas' aerated rubber soles are seen as key to the brand's success and their manufacturing process is kept under strict wraps.

Beyond acknowledging they're made from a mixture of domestic and imported rubber that shrinks and hardens with extended wear, Porto declined to provide any details about the secret soles.

In the beginning, Havaianas came in a Spartan palette, their white soles paired with either sky blue, black or yellow straps. Sold in popular street markets, they quickly became such a basic for the poor here that they were included on the list of basic necessities such as rice and beans that the government used to calculate cost-of-living increases.

"Havaianas were almost synonymous with poverty," said Porto. "They were sold like a commodity, with no investment in design or marketing or innovation, and the whole business model hinged upon selling increasing numbers of pairs in order to drive production costs down."

By the early 1990s, with domestic competitors beginning to eat away at Havaianas' market share, label executives made a bold, 180-degree shift in strategy. Their plan, aimed at rebranding Havaianas as a fashion accessory, would prove so wildly successful that it has since become a business school case study in marketing.

The label looked to inventive wearers who had long been transforming their bicolour sandals into single colour ones by flipping the white-topped sole over. In 1994, Havaianas introduced a new line of one-shade sandals in black, royal blue, pink and purple.

Suddenly, middle- and upper-class Brazilians who either wouldn't have been caught dead in Havaianas or donned them exclusively for the short trek from their beachfront apartments to the sand, were snatching them up in multiple shades for all occasions.

Ladies who lunch from Rio's tony Leblon neighbourhood wear them to all-important visits to the hairdresser or even out on dates. Private school scions use them to mark the goal box during beach soccer matches. Moneyed businessmen wear them while walking the dog or out to a high-end "churrascaria" barbecue.

Havaianas now come in an ever-changing rainbow of 23 shades, some emblazoned with eye-popping prints on the soles or rubber appliques on the straps. At the brand's concept store on Rua Oscar Freire, Sao Paulo's answer to 5th Avenue in New York, Havaianas devotees can get bespoke sandals made to their colour specifications or emblazoned with their initials.

Swanky Brazilian jewelry label H. Stern has crafted a limited edition of six pairs bedazzled with diamonds and glinting with gold. Designer Gustavo Lins, a Brazilian who's among the elite cadre of Paris' haute couture purveyors, sent out a collection of made-to-measure garments paired with Havaianas. The brand has also collaborated with Missoni to create a line of flip-flops emblazoned with the Milan-based luxury label's hallmark zigzags.

While prices for the basic, no-frills models have remained low, retailing in Brazil for just $5, a premium off-the-shelf pair goes for up to $28 here. In the U.S. most models are in the $20-$30 range.

Brazilian-born former model and socialite Andrea Dellal keeps her dazzling Rio apartment stocked with Havaianas in every conceivable size and colour.

"I keep baskets full of them in all the bedrooms, and my guests and my children and their friends help themselves," said Dellal.

She said she had vivid memories of wearing Havaianas to the beach as a child. Now she wears them everywhere.

"I wear them with my Dolce & Gabbana dresses during the day because they're easy to run around in and sometimes I wear them at night with long dresses. I love the look," said Dellal, whose other footwear of choice includes vertiginous heels by Manolo Blahnik and daughter Charlotte, who's behind the high-end London shoe label Charlotte Olympia.

Still, despite, or perhaps because of, their adoption by the elite, Havaianas continue to appeal to their original customers at the bottom of Brazil's class hierarchy.

"The popular classes are buying more Havaianas than ever," said consultant Porto. "Poor people have the right to be fashionable too, and people in this group tend to save up for different models and lots of colours.

"They see their bosses wearing Havaianas, they see TV stars wearing them and even foreign movie stars in them, and they feel proud to wear them."

A single factory in the northeastern state of Paraiba churns out all those flip-flops, but a new site is under construction in central Minas Gerais state to keep up with demand.

The brand is looking to grow in other emerging countries, such as China and India, but its core will remain unapologetically Brazilian, Porto said.

For working-class Brazilians, who were the reason for the brand's initial success, anything less would be unthinkable.

"I have been wearing Havaianas ever since I can remember," said Vania Lucia Ribeiro, a 32-year-old maid who lives in a distant Rio de Janeiro suburb. "I buy them for my children and I buy them for myself. I can't imagine living without them."