One of the episodes of the Netflix documentary series "Unwell" gives a very interesting overview of bee sting therapy. One doctor talks about its effectiveness against arthritis, because the body releases cortisol and analgesics in response to the bee venom, which explains why people with arthritis feel better.

However, the next point made is that a more straightforward way to achieve a similar result would of course be to inject the cortisol directly, instead of provoking this response by the body by injecting toxins first.