I've done a bit of reading on the subject since. Here's one physician's explanation of the practice:
I am always desirous that the patient's hair should be cut off. The mere removal of it is often attended with benefit; the headaches and confusion of thought are relieved, and the patient is calmed. We can then also, with much greater convenience and effect, apply cold washes to the head. Patients sometimes demur to this shaving of their heads: but they generally consent if you explain to them that their hair will at length fall off, in consequence of the fever; and that the head, if on that account only, had better be shaved at once.
~ Lectures on the Principles and Practices of Physic. Delivered at King's College, London, by Dr. Watson. The London Medical Gazette. Friday August 26, 1842
|Apothecary workbench. Photo by Cybjorg, via Flickr|
My hair didn't "at length fall off" after all, I'm relieved to say. Though a few extra pounds may have (I'm also relieved to say).