An Extremely Painful Procedure
While a boy's body is developing in his mother's womb, his foreskin forms while being initially fused to the glans, similar to how a fingernail is fused to the underling nail bed. It naturally remains this way until the child is several years old, sometimes even until puberty. Thus, the first step in an infant/childhood circumcision is to forcefully separate the foreskin from the glans by inserting a probe and ripping that adhesive membrane -- think of jabbing something under your fingernail until it pops off. Obviously this is very painful, and it is just the beginning. Then comes the crushing, clamping, and slicing.
The pain of circumcision can be so intense that many babies go into a state of shock. Naive parents can be convinced that "he slept right through it," when in reality his body may have started shutting itself down because of the massive trauma just inflicted upon him. Although not yet fully studied, there are indications that this flood of stress hormones through the body could have an impact on brain development during this very crucial period, just hours to days after birth.
Pain Prevention: is it even possible?
Before the procedure begins, a doctor may apply a topical anesthetic cream or administer a "dorsal penile nerve block," an injected mild local anesthetic. Both would possibly help block some of the pain of the procedure, IF there is a long enough waiting period to give the medicine time to build up to full effectiveness. However, the doctor will usually continue on with the procedure as quick as the next instrument can be picked up. There is also some concern that these anesthetics are not completely safe for use with infants, particularly on their genital area.
Some doctors perform the operation with only a sugar water pacifier, in an attempt to increase endorphins and distract from the pain.
The Pain Lingers
Once the operation is complete, the pain can linger for hours, sometimes days. Until the circumcision wound completely heals, it will be subjected to various painful situations such as being exposed to urine and feces, and being touched / rubbed by his diaper and clothing. Sometimes even simply being exposed to the air during diaper changes can be painful. Even after the wound is healed, the glans - which is supposed to be a semi-internal organ - continues to experience pain since it is now constantly exposed to abrasion on clothing. Eventually, over the course of several years, the skin of the glans becomes keratinized and thickened (similar to a callous) as the body finds a way to block this constant sensation.
Life-long Painful Complications
Many complications are possible from infant circumcision, some of them can cause long-term pain. For example, if too much skin is removed,& erections can make the remaining skin painfully tight, possibly even causing tears. Sometimes these complications do not show up until puberty, when there is not enough skin to accommodate the growth of the penis during this time. A child is unlikely to report these kinds of problems to his parents, so they may be completely unaware and believe he is happy they had him circumcised.