[red-iron-pine]

Ergot-ism.

Ergot is a fungus / mold that grows on grain, esp. types of wheat or rye. Rye in particular has a reputation. A whole towns supply of grain gets wet -- bad rains after harvest -- and everyone catches the ergot poisoning.

The toxins produced by ergot are vasoconstrictors -- they can often choke off blood pumping enough to cause gangrene in the weak / old / sick. Moving a lot, i.e. "dancing" forces the blood to pump harder and keeps your toes from dying from lack of oxygenated blood.

Ergot also contains a precursor to LSD, and is said to correlate with hallucinations. LSD itself was discovered by scientists trying to isolate ergot toxins for medical vasoconstrictor use (e.g. give a small dose to a surgery patient or something to minimize bleeding).

But basically your extremities are desperate for blood and you're tripping balls so you dance, move, etc. just to keep going.