The friction inside your shoe causes dead skin to flake off . The particles of dead skin contain organic material which gets pushed to the side of the shoe between the upper and the sole where in the ideal conditions of sweat and warmth decomposition occurs causing malodours.
By spraying SportsPONG Foot & Shoe Spray lightly inside the shoe the enzymes and good bacteria remove the smell. Take care not to let the shoes dry in sunlight.
If the socks you use contain a mix of Lycra wash them in SportsPong.
SportsPONG Foot & Shoe Spray is free of phosphates and phenals.