Usually, blisters inside the foreskin may be caused by skin allergy, foreskin blisters, genital herpes and so on. 1. Skin allergy: If the patient is allergic to certain drugs or food, it can lead to blisters in the foreskin, or the genital area is in contact with allergens that are easy to trigger allergy, which can also lead to blisters in the foreskin. 2. Foreskin blisters: usually due to penile infection, inflammation, penile skin lesions or irritation caused by the penile area, usually the foreskin area of the blisters of varying sizes, which may be accompanied by pain, itching, burning sensation. 3. Genital herpes: mainly caused by herpes virus infection, usually small blisters appear in the genital or perineal area, men are more likely to be found in the foreskin, glans, coronary groove and other parts of the body, which may be accompanied by pain and discomfort. The blisters inside the foreskin may also be caused by other reasons. It is recommended that the patient should consult a doctor in time to clarify the cause of the disease under the doctor’s guidance in order to take corresponding treatment measures.