Large blisters on the penis may be caused by overstimulation, prepuce glansitis, genital herpes and other factors. 1. Overstimulation: for example, frequent masturbation or excessive squeezing of the penile area may cause tension blisters to appear locally on the penis, accompanied by tingling, redness and other symptoms. 2. Inflammation of the foreskin and glans penis: when there is a localized infection of the penis, it may cause inflammation of the foreskin and glans penis, and when stimulated by inflammatory substances, it may cause localized blisters to appear, which may be accompanied by itching, ulceration, oozing and other symptoms. 3. Genital herpes: usually caused by herpes simplex virus infection, belongs to a sexually transmitted disease, so that the penis and the scrotum and other parts of the blisters, accompanied by tingling, and has a strong contagious. If there are large blisters on the penis and other abnormalities, it is recommended that you seek medical attention for appropriate examination and treatment to avoid continued aggravation of the lesions.