Dermatologist Catherine Faulkner said thongs left their wearers dangerously exposed to skin cancer and people should check not only the tops of their feet but also their soles and underneath nails for suspicious signs, she was quoted by 'Courier Mail' newspaper here.

"Often sunscreens are washed off the top of the feet when people walk through water, so we do see quite a lot of skin cancers on the top of the feet," she said.

"The real danger is under the feet because it's not a place you look. It's also where you get this dangerous and more aggressive melanoma, which is often diagnosed late," she added.

The other body parts often forgotten when applying sunscreen are the lower lip; scalp; tops of the ears; and the area between the nose and eyes.