Flip-flops and sandals: why some summer footwear styles can hurt your feet

Summer wardrobes fill up with flip-flops and slide sandals, but foot specialists say not all of that lightweight footwear treats feet kindly. Podiatrists have long flagged flat, backless sandals as a seasonal source of heel pain, blisters and tendon strain, and the warning resurfaces every year as flip-flop sales spike with the temperature.

The problem starts with how these sandals stay on the foot. Because there is no strap around the heel, the toes have to grip and curl slightly with every step to keep a flip-flop from sliding off. Repeated thousands of times over the course of a walk, that gripping motion recruits small muscles and tendons in the foot and lower leg that are not built for constant, active work.

Over days or weeks, that extra strain can inflame the plantar fascia, the band of tissue running along the sole of the foot, producing the stabbing heel pain associated with plantar fasciitis. It can also aggravate the Achilles tendon and the small flexor tendons in the toes, particularly in sandals with completely flat, unsupportive soles.

Flat, thin soles carry a second problem: they provide little cushioning or arch support, so the impact of each step travels more directly into the joints of the foot, ankle and knee. Podiatrists say this matters most for people who wear flip-flops for hours of walking or standing, rather than a short stroll from a beach towel to the water.

Open-backed, backless designs also leave the foot more exposed. Without a covered toe box or side panels, feet are more vulnerable to stubbed toes, cuts and sunburn, and the constant exposure of the heel to friction against a hard sole can dry and crack the skin over a season of wear.

None of this means every sandal is a health risk. Specialists distinguish between minimal flip-flops, cheap and completely flat, and more supportive slides and sandals built with a contoured footbed, a defined arch and a strap that secures the heel or ankle. Those features spread pressure more evenly across the foot and reduce how much the toes have to grip to keep the shoe in place.

Simple checks can help shoppers tell the difference in a shop. A sandal that bends easily in half at the middle, rather than only at the toes, usually lacks the structure needed to support the arch. Pressing a thumb into the footbed to see whether it springs back, rather than staying flattened, is another rough test for cushioning quality.

How the sandals are used matters as much as the design itself. Podiatrists generally suggest reserving very flat, minimal sandals for short trips, such as walking to a pool or beach, and switching to more structured shoes for a full day of sightseeing, errands or standing at work.

People with existing foot conditions, including diabetes, plantar fasciitis or bunions, are usually advised to be more cautious with unsupportive sandals, since reduced cushioning and grip can worsen existing pain or, for people with diabetes, raise the risk of unnoticed cuts and blisters that are slow to heal.

The seasonal advice, in short, is not to abandon sandals but to choose and use them deliberately: save the flattest, cheapest flip-flops for brief wear, look for models with arch support and a secured heel for longer days on foot, and see a podiatrist if heel or arch pain persists for more than a couple of weeks.