Hi. Thanks for your query. Noted the history about your son who has undergone circumcision n past and now have white greasy substance coming out of a small spot that goes all around the head of his penis. When you start cleaning it starts coming out of this spot but it is a lot of it still inside. This is a classical history where a sinus has developed during the healing stage after the circumcision. The healing is very fast in children. The sweat that occurs at this junction called corona has a white material in it and is called smegma. It is this white material that gets retained as the water in it evaporates. I would advise you the following in such a situation. Try to pull up the skin fold under which the smegma is accumulating. In many cases of small children there can be pealing out the opposing surfaces of the skin and the problem is solved as there ill not be any sinus at all. If this can not be done due to dense adhesion as small surgical correction will solve the problem for lifetime. So do not worry, this is fully treatable.