The abnormal sensation of insects, especially ants, crawling on or under the skin when nothing is actually there.
From Latin 'formica' (ant) + '-ation' (noun suffix). Coined in medical terminology around the 1700s to describe this hallucinated tactile sensation, using the ant metaphor because the crawling feeling resembles ant movement.
Formication is one of those wonderfully specific medical terms that turns a disturbing symptom into something almost poetic—and it's much more common than you'd think, affecting people with diabetes, withdrawal from stimulants, and even certain psychiatric conditions.
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