Urbanangler, folks might shoot me for this but this is how it really works. Your body gets invaded by some kind of infection. The white corpuscles attack this intruder with killer force and this happens everyday without us ever knowing about it. Sometimes, an attacker is either too strong or our bodies have been weakened through lack of sleep or whatever. When this happens, the whites attack but can't kill everything and simply imprison them (in the glands) to deal with them later. This almost always is dealt with by the whites without antibiotics.
If it persists, have it checked out.