I'd be more likely to believe (at least part of) the effect is caused by giving the natural defense systems of the body something actually foreign to 'attack'. Sort of like regular training exercises and legal explosives/fireworks days give a more controlled and thus safer expression of pressure relief, training, and general readiness inspection.

PS: Related to the fireworks I mentioned, I'm for having local fire departments provide basic fire knock back training with basic safety gear (bucket of water and hose) that should be required when they're in use. We focus way too much on black and white bans rather than enforcing responsible consumption.

Anecdotally, I'm reminded that for constipation, Gandhi followed Adolf Just’s prescription of applying to the abdomen a bandage of clean earth moistened with cold water and spread like a poultice on fine linen. This I applied at bedtime, removing it during the night or in the morning, whenever I happened to wake up. It proved a radical cure.