Plugged ears are usually caused by a buildup of cerumen in the auditory canal. Cerumen is the fatty, yellowish substance secreted by the ceruminous glands in the external auditory canal. Normally, it flows out of the auditory canal spontaneously. It is responsible for trapping impurities and eliminating them toward the outside. It also protects the cutaneous covering of the outer ear against infections. In addition, cerumen serves to lubricate the eardrum, which would be hard and rigid otherwise. Unlubricated, the eardrum would not be able to transmit sound efficiently.