The hard and thick corns on the soles of the feet are commonly caused by physiological and pathological factors. 1. Physiological factors: the main consideration is that there is long-term mechanical friction on the soles of the feet, especially for manual laborers, in their daily work, excessive pressure and friction on the soles of the feet can lead to abnormal proliferation of the stratum corneum on the soles of the feet, and so it becomes hard and thick. 2. Pathologic factors: (1) palmoplantar keratosis: a group of chronic skin diseases characterized by diffuse or limited thickening and hyperkeratosis of the skin in the palm or plantar area, usually caused by congenital factors. (2) Keratosis pilaris: a type of chronic eczema. When keratosis pilaris occurs on the soles of the feet, it can lead to localized hypertrophic erythema with itching and erythematous lesions, so the stratum corneum on the soles of the feet can become hypertrophic, rough, and covered with scales. (3) Erythema keratosum: it is a genetic disease caused by gene defects or gene mutations, which can lead to the appearance of red patches and keratinized scales on the local skin of the patient, especially the symmetrical progressive erythema keratosum, which can lead to keratinization of the skin of the toes and other parts of the skin, and the stratum corneum can become hard and thick. Therefore, once the phenomenon of hard and thick stratum corneum on the soles of the feet occurs, it is necessary to go to the hospital in a timely manner to find out the specific cause of the disease and then carry out reasonable treatment.