Ballooning is a normal and harmless occurrence for many intact boys. At birth, the foreskin is fused to the glans (head) of the penis by a delicate epithelial membrane. This shared layer dissolves naturally over time due to hormonal changes and natural exploration. Eventually, the boy will be able to retract his foreskin completely once the membrane has fully dissolved.

During the course of membrane dissolution throughout the early years of a boy’s life, urine can momentarily swirl around underneath the foreskin in spots where it has already separated from the glans. It is not unusual for urine to fill up these pockets between the foreskin and glans briefly during urination. This is often referred to as “ballooning” because it appears as just that: a balloon being blown up, then deflated.

‘Ballooning’ of the foreskin is a natural and normal event that happens with some intact boys. . . . [When] the boy pees, the urine can sometimes briefly inflate the pockets where the foreskin has naturally detached.
— Doctors Opposing Circumcision

The foreskin contains muscle tissue that helps keep its tip (preputial opening) closed, except when passing urine, in order to keep contaminants out. This muscle relaxes quickly in response to the pressure of the urine behind it, and the “balloon” deflates as the urine exits the body. The slight pressure the urine creates in these pockets before exiting helps further dissolve the fused membrane, aiding the separation process. 

As the foreskin attachments to the head of the penis begin to separate naturally as the little boy grows, sometimes pee fills these new spaces and creates ballooning, which is a normal developmental process that is seen in many little boys.
— Dr. Adrienne Carmack, Urologist, Author of The Good Mommy’s Guide to Her Little Boy’s Penis

There is no need to panic if you notice your son’s foreskin ballooning. Parents might observe ballooning when changing a diaper or while the boy is learning to use the potty/toilet, or they may never observe it! Ballooning does not occur in all boys.

Ballooning is normal, though it can be alarming to parents seeing it for the first time. . . . If your son is not in pain and his urine is flowing freely, there is no need to worry.
— Intact America

If you observe ballooning in your own son and there are no other concerns (e.g., ongoing pain, discharge, or the urine not exiting), no action is required. You can rest assured knowing that his body is doing what it was designed to do.

Last updated 8.25.19.