Nail fungus infection usually starts with the toes. At first you might just notice some puzzling yellow discoloration of a toenail. What you won't see is the network of fine fungal mycelia (like branching stalks) that are spreading out in the sheltered tissue under the toenail.

The fungal growth tends not to spread into the tissue of the toe, at least not right away. Your body's immune system is holding it at bay. Rather, it grows through the matrix of the toenail, getting nutrients from keratin, a protein found in toe- and fingernails. Nails are not living tissue, and they don't produce an immune response to the invader, so a nail fungus infection can get well established in the toenail before you even know it's there.

What would the world do without nail varnish? Just think of all the unshiny, terrible looking, uncolourful nails we'd all have to put up with! It'd be a disaster.

Well, alright, so I'm not entirely serious, but nail varnish does have some point beyond making nails look pretty. Many nail varnishes also contain substances that will protect your nails, by stopping them from breaking and making them taste nasty so you don't bite them. Some even claim to make your nails grow faster.