Breathable shoes only work with functional socks. Cotton socks store moisture. In contrast, functional socks remove the moisture from the feet to the outside. Then the breathable shoe membrane comes into play and transports the moisture to the outside of the shoe. Therefore the principle behind breathable shoes only works if breathable socks are worn. Only a combination of functional socks and breathable shoes effectively removes sweat sending it to the outside of the shoe. This is the principle of breathability.