Corns mostly appear on toes, due to pressure
Medical illustration of a corn
If the skin is exposed to permanent pressure and friction e.g. from ill-fitting shoes, it reacts by building up this outer layer, thus forming callous skin (see also: Instant help for dry and calloused skin). If the pressure persists, especially in a specific spot, the callous skin can form a corn with a hard core that reaches the deeper, sensitive skin structures and thus causes pain. This core is often called the „root” of the corn.
Corns can appear either as white/ gray or yellow/ brown in colour depending on your skin type. Symptoms include pain and swelling around the corn and discomfort with direct pressure when walking.
Corns mostly occur on the top of the toes and on the outside of the fifth toe, i.e. the areas where there is the most pressure from the shoes. The most painful form of corn is the type where the corn becomes entwined with the nerves of the skin.
Corns can also occur at the sole of the foot and as so-called soft corns in between toes where the skin is moist from sweat or inadequate drying.