The yellowing of the soles of the feet with hard skin may be related to fungal infections, metatarsal warts, palmoplantar keratosis, callus and other conditions. 1. Fungal infection: If the soles of the feet are infected by fungi, tinea pedis will be formed, tinea pedis patients will have obvious itching symptoms, the skin becomes red and thick, with the aggravation of the condition, the skin in the area will become rough and cracked and yellow. 2. metatarsal warts: If the soles of the feet are infected with human papilloma virus, metatarsal warts may be formed, manifesting themselves as small bumps slightly above the surface of the skin, the bumps are yellow, the skin is hard, and there may be black dots in the middle of the bumps. 3. Palmoplantar keratosis: mostly related to heredity, the disease may be induced by excessive local skin friction and chemical stimulation, which may lead to hyperkeratosis of the skin in this area, accompanied by yellowing and thickening phenomenon. 4. Callus: also known as callus on the soles of the feet, usually on the soles of the feet or joints, the skin in this area will be thickened, and hardened and yellowed. Considering the causes of the disease, patients should consult a doctor in time to do a systematic examination.