Fungal Nail Infection
If your nail has changed colour or has become brittle and lifted away from your nail bed, you could be dealing with a fungal nail infection. Fungal nail infections usually happen on your toenails, as warm, sweaty socks and shoes can give fungi just what they need to thrive, but they can affect your fingernails too.
This is why many people pick up fungal nail infections after they’ve been to the gym, especially if you’ve been walking around barefoot in the changing room and then popping on your sweaty gym shoes. Those trainers are like a holiday home for the fungi that cause infections.