] Red flannel was thought to be especially effective, on some sort of colour therapy principle, no doubt.

Not long ago, I ran across a biography of Elizabeth I in which the biographer described her brush with smallpox. No one wanted to believe the physician when he diagnosed it, and he was packed off rather unceremoniously, only to be hauled back when it was thought the queen was dying and he might be able to help. Part of his cure was to have her wrapped in red flannel--yes, he specified red flannel--and placed in front of the fire in her chamber. The queen recovered, with minimal scarring.

I wonder if that "colour therapy principle" was part of this plan--whether the physician and his cronies would have believed that red flannel was particularly effective with this illness because there might be some sort of connection between the red flannel and the red of smallpox inflammation, etc. Maybe it would also work well for red measles? ;-)