If my son had a tonsillectomy and adenoidectomy, why does he now have white mucus?

Protective: That's his body's way of protecting the surgical site.

How long after?: How long ago did your son have his t&a surgery? Where is the mucus you are seeing? It is not unusual to see cream to white colored material (fibrinous exudate) on the tongue, palate and back of throat for up to 2 weeks after tonsil surgery. Check with your son's surgeon to be sure there are no other issues.