A white blister on the foreskin of a child may be caused by genital herpes, torticollis, eczema, etc. Further differential diagnosis by a doctor is required. 1. Genital herpes: a sexually transmitted disease caused by herpes simplex virus (HSV), which can also infect newborns through the placenta and birth canal, leading to congenital infection in newborns. It can be manifested as clusters or scattered small blisters around the external genitalia or anus. 2. Foreskin glans infection: If the foreskin or glans is infected by bacteria and other pathogenic bacteria, it can cause inflammatory reaction and white herpes may also appear. 3. Eczema: Eczema is an inflammatory skin reaction with intense itching caused by a variety of internal and external factors. Acute eczema can be manifested as dense corn-sized papules, papules or small blisters, so if the foreskin is suffering from eczema, white blisters may also appear. There are many reasons for a white bubble on the foreskin of a child, it is recommended that parents take their children to the hospital in a timely manner, to clarify the cause of the disease, and standardized treatment under the guidance of the doctor, so as not to delay the condition of the body to bring about adverse effects.