Red spots on the sole of one foot may be due to syphilis rash, eczema or allergies. 1. Syphilis rash: Syphilis, if not treated in time, enters the second stage of syphilis, resulting in generalized syphilis rash, causing skin and mucous membrane damage on the soles of the feet. It can be manifested as rose-colored erythema on the soles of the feet, usually without obvious self-conscious symptoms, no itching, pain and so on. 2. Eczema: Eczema is a kind of inflammation caused by a combination of internal and external causes, such as infection, immunity and other factors. Inflammation leads to damage to the skin barrier, which is characterized by small pimples in the early stages and red spots in the later stages. 3. Allergy: Due to drugs, infections, shoes, socks and other materials that are irritating, resulting in an allergic reaction to the skin, which can be manifested as flaky edematous erythema and may be accompanied by itching. When there is a red spot on the palm of one foot, it is recommended to consult a doctor in time, follow the doctor’s instructions for further examination, clarify the cause with the help of the doctor, and carry out targeted treatment or therapy.