Culpeper placed the onion under Mars, the hot and fiery planet, an obvious reading of its heat and its power to sting the eyes. In European folk practice the onion was a protective plant that absorbed sickness and evil: a cut onion was left in a room to draw off disease, hung in the house to take up infection, and used in charms to banish harm, the vegetable read as a sponge for whatever was malign. Its meanings run in two channels, the Egyptian eternity of its endless layers, and the folk role of a fiery bulb that draws off and destroys what is unhealthy, both grown from the plain nature of a pungent, many-coated root.
Onion skins, saved and boiled, remain the traditional dye for Easter eggs across Ukraine, Poland, Russia and much of Eastern Europe, producing a rich gold-to-mahogany colour without any synthetic dye, a genuinely living seasonal practice that turns the humblest kitchen scrap into part of a religious festival. Modern food science has also confirmed that onion contains genuine antimicrobial compounds, part of why it was historically valued as a preservative and a folk defence against spoilage and infection long before the word bacteria existed, a case where an old protective reputation and a measurable chemical property point in the same direction.