Calluses and corns are often caused by a deformity of the feet or toes. Unsuitable footwear can also cause chafing and pressure, resulting in the skin growing thicker. The callused area is sensitive to ulcers.
You can treat calluses and corns by massaging moisturiser to the areas and wearing proper shoes. You can also protect the callused area with superlon tube, which can be bought for example from pharmacies. A podiatrist can remove the callus or corn and find out the underlying reason for callus formation.