I'm interested in rheumatism, having seen relatives suffer badly from it, so I was interested to stumble accidentally across the following observations made in New Zealand in the 1920s/'30s:
'Speaking to an Auckland bee-keeper, he said that before keeping bees he had had rheumatics badly for many years. When he started keeping bees he got stung by them a great deal, and this soon appeared to have cured his rheumatics. He had lost it entirely.'
The source is Crook Frightfulness, by 'a Victim' (Birmingham: J.G. Hammond, n.d.), p.63. The book is a rather strange little memoir by a former rent collector who became convinced that he was being pursued globally by villains employing ventriloquism (amongst other things) to menace him. The less frenzied tone of offhand remarks like this one - exactly the sort of folkloric item one picks up in casual conversation - suggests they are rather more reliably related than all of his stories of corner-of-the-mouth insults.
A quick online search now reveals that there is some scientific literature on the subject, pointing to proper investigation of folk remedies. (A very brief scan suggests the scientific jury is still out, at best, but that might also highlight the attractiveness of the treatment as a folk remedy).