Ergot poisoning and Religion

[Smaug]

From what I've read convulsive form of ergotism is considered as one of the causes of St. Vitus' dance (the wiki arcticle itself lists drug poisoning among 'other causes'). Mid-19'th century research done in afflicted rural settlements in Russia describes fitting symptoms and behaviour. However, I won't argue against other factors or combination of them being able to cause St. Vitus' dance, too.

I agree, there are similarities. FYI, St Anthony's is also tied to erysipelas, a strep condition where the skin appears red and inflamed (fire?). 

Ergot is also linked to the Salem witch trials, but I'm not sure how accurate that connection is.

Technically, St. Anthony's fire (sometimes also holy fire - 'ignis sacer') was a reference to gangrene in general (both dry and wet). But it was most commonly associated with what is nowadays known as gangrenous ergotism. Ergot contains a chemical that causes vasoconstriction so consuming contaminated bread gradually leads to dry gangrene. It begins with tingling in an affected limb which transforms into increasing burning sensations. Finally the limb 'burns off' turning black and falling off due to necrosis. 'Holy fire consuming the victims' members' leaving dead and amputees was a common contemporary description.

Speaking of the skin condition, I came across erysipelas being called St. Anthony's fire as well but it wasn't the main meaning.

Regarding St. Vitus' dance, I've read a hypothesis that in certain cases it may have been triggered by an urge to get rid of the tingling sensations in the limbs which were caused by poisoning. It's not hard to imagine how this could escalate into an act of mass hysteria, given the hallucinogenic effect of ergot poisoning and overall mentality. This does not cancel out the other hypotheses of couse. They could have also been interwined in the most crazy ways.