A blister-like thing on the outer urethra may be related to causes such as glans circumcision, urethral cysts, and genital herpes. 1. Foreskin glans inflammation: If the foreskin or glans is infected by bacteria and other infections, it can cause pimples and pimples at the external urethral opening. 2. Urethral cysts: cystic swellings may appear on the mucous membrane near the external urethral opening with a smooth surface. 3. Genital herpes: herpes and ulcers may appear at the urethral opening, which may also be accompanied by pain and abnormal sensation. To sum up, it is recommended that the person who has a blister-like thing on the external urethra go to the hospital in a timely manner to clarify the cause of the disease and carry out standardized treatment under the guidance of the doctor, so as not to delay the condition to bring adverse effects on the body.