Each morning, as I sit on the London Underground and am forced to lift my eyes away from the comfort of my phone screen (the service isn’t great down there), I find myself staring at everyone’s hands.

Medically reviewed by Amelia MacIntyre, DO Mycosis nail fungus, also known as onychomycosis, is a fungal infection of the nail unit. It is more common in the toenails because fungi thrive in warm, ...