Clinical case review

A delusion of infestation

John Ellard



One of my middle-aged patients, well known to me, has come to me to complain that there is an ants’ nest in his head. I have looked in both his ears with an auroscope and have told him firmly that his ear drums are intact. Ants could neither enter nor depart from his head, and his belief is quite impossible. He remains totally convinced that they are there.

Article Extract


Delusions of infestation are uncommon but do turn up from time to time. The sufferers consult general practitioners, dermatologists and other specialists appropriate to their belief; they do not come to see psychiatrists. Ants and lice are common agents of infestation. The sufferer may present a matchbox with cotton wool in it, in which are to be found dead ants and other small objects gathered from his or her surroundings, which provide – for the sufferer – absolute proof of the complaint (Figure).