The cause may be due to mosquito bites, hand, foot and mouth disease, eczema and other factors. 1. Mosquito bites: Mosquitoes will release saliva when they bite the skin on the back of the foot, leading to an immunopathological reaction in the body, and red bump-like pimples or blisters may appear on the back of the foot. 2. Hand, foot and mouth disease: the disease is usually caused by the Coxsackie virus, the patient’s hands, feet, mouth, buttocks and other parts of the skin lesions such as maculopapular rash, pimples, herpes, and other skin lesions, and in severe cases, it will lead to central nervous system damage. 3. Eczema: the disease is related to abnormal immune function, skin barrier dysfunction and other factors, including acute eczema, subacute eczema and chronic eczema patients, may appear pimples, blister-like skin changes, accompanied by itching. 4. Pressure purpura: The disease is related to gravity, venous insufficiency and other factors. Patients may have pinpoint-sized, clustered or scattered petechiae on the instep. There are many factors that lead to red dots on the dorsum of the foot, and it is recommended to go to the hospital in time to identify the cause of the disease and carry out the relevant treatment, and strictly comply with the doctor’s instructions for the use of medication.