(CNN) -- King Tut wore them. So did Cleopatra. Members of the 2005 Northwestern University's women's lacrosse team sported them at the White House.
Especially in the dog days of summer, people everywhere seem to be tossing their closed-in shoes for cool, convenient pairs of flip-flops. But many foot doctors say that when it comes to healthy feet, the lightweight sandals can be a flop.
"If you wear them all the time, they aren't good for you," says Dr. Kathya Zinszer, associate professor of podiatric medicine and director of community outreach at Temple's School of Podiatric Medicine. "They are terrible for the arches. They give you no support and they don't protect your feet."
"I'm not totally against flip-flops," she says, "but they can be dangerous."
Since the days of the Pharaohs, flip-flops, also known as zoris, thongs, slip-slops, slides and slaps, have traditionally been the shoe of choice on hot days when the tootsies could use a breather. Ask flip-flop aficionados why they love them and the answers are pretty much the same. Comfort.
"I have to wear heels all the time at my job," says Shehawnee Prescod of Atlanta, Georgia. "But I always keep a pair of flip-flops in my car."
David Henson, also from Atlanta, would never give up his Gucci flip-flops. "They're Italian, leather, cushy and really comfy, " he says with a smile.
Podiatrists say people who have flat feet or other foot issues should wear a more structured shoe. That's because walking in flip-flops can be tough on the structure of the foot. According to a 2008 study from Auburn University, researchers found that wearing thong-style flip-flops resulted in pain in the ankles, legs and feet. The investigators found that flip-flop wearers took shorter steps and that their heels hit the ground with less vertical force than when the same walkers wore athletic shoes.
When wearing flip-flops, the study participants did not bring their toes up as much during the leg's swing phase, resulting in a larger ankle angle and shorter stride length, possibly because they tended to grip the flip-flops with their toes. This repeated motion seemed to result in problems from the foot up into the hips
The American Podiatric Medical Association warns that because flips-flops have no backing they can catch on to things as they flip and flop. That may cause people to fall. So the association strongly recommends that people not play sports in flip-flops or do any type of rigorous outdoor activities, including cutting the grass, when they wear these shoes.
"You need to make sure that you are securing the biomechanics of your foot. So if you just get what people call slides, or rubbery flip-flops, it is more dangerous than trying to do something barefoot," notes Zinszer.
Doctors will say comfortable flip-flops can be worn occasionally, but how well the feet hold up in them varies. Although the podiatric medical association doesn't discourage the wearing of these tiny treads, it warns that people with circulation issues or diabetes, who generally have poor feeling in their feet, should avoid flip-flops. Physicians say it's too risky for getting injuries that could become infected.
"The shoe really doesn't protect your foot," explains Zinszer. "So you can get scrapes, bruises, small lacerations that in many cases can lead to more serious problems."
Philadelphia native Deborah Brooks, a patient of Zinszer, has sensitive feet and needs to take care of them. She loves her flip-flops because as she put it, "You just slip your foot in and you're gone." But Brooks developed a blister around the thong part of her rubber slides. So Zinszer told her to ditch the shoes for a sturdier pair.
"They cause ankle sprains, because your feet slide in them, warns Zinszer. "And that can also cause blisters and calluses that could fester."
Zinszer also mentions that some of the cheaper flip-flops can actually carry foot diseases, such as athlete's foot, from one summer to the next.
But there are some positives to wearing them too. Many doctors recommend flip-flops be worn in public showers, like those at the gym, to avoid skin diseases. For example, flip-flops are used in some branches of European and North American military to slow the spread of fungal infections.
And they can help with arthritic joints. A recent study conducted at the Rush University Medical Center in Chicago, Illinois, found people who had arthritic knees had less stress on their joints wearing flip-flops than other types of shoes. And although the researchers did not advocate wearing flip-flops all the time, they did think the flatness and the flexibility seemed to ease the stress on the joints.
Still don't know if flip-flops are right for you? The podiatric medical association's website offers a list of flip-flop suggestions and guidelines on how to wear them. Zinszer says even the new Fit Flops are better for you. "They are a little more accessible for the biomechanics for the foot," she says, "They're going to give you some activity, without having that lack of support."
"A lot of my patients ask, do they tone your legs and your tush like they say they do?" she says with a smile. "I say, the jury is out on that, but I doubt any shoe, even a flip-flop, can replace the gym."
CNN's A.J. Willingham contributed to this report.