Phimosis (from Greek φίμωσις phimōsis 'muzzling'[9][10][11]) is a condition in which the foreskin of the penis cannot stretch to allow it to be pulled back past the glans.[3] A balloon-like swelling under the foreskin may occur with urination.[3] In teenagers and adults, it may result in pain during an erection, but is otherwise not painful.[3] Those affected are at greater risk of inflammation of the glans, known as balanitis, and other complications.[3]

In infancy, phimosis is considered physiological (normal).[11] At birth, the foreskin is naturally adhered to the glans, and cannot be retracted. As the child ages, in most cases, the foreskin will naturally detach. In young boys, it is normal not to be able to pull back the foreskin at all.[7] Over 90% of cases resolve by the age of seven, although full retraction is still prevented by balanopreputial adhesions in over half at this age.[5][7] Occasionally, phimosis may be caused by an underlying condition such as scarring due to balanitis or balanitis xerotica obliterans.[5] This can typically be diagnosed by seeing scarring of the opening of the foreskin.[5]

Generally, treatment isn't considered necessary unless the foreskin still cannot be retracted by the age of 18.[4] Efforts to pull back the foreskin during the early years of a young male's life should not be attempted.[7] For those in whom the condition does not improve further, time can be given or a steroid cream may be used to attempt to loosen the tight skin.[7] If this method, combined with stretching exercises, is not effective, then other treatments such as circumcision may be recommended.[7] A potential complication of phimosis is paraphimosis, where the tight foreskin becomes trapped behind the glans.