Here are the most common reasons, rooted in both tradition and some science:
1. To Freshen and Disinfect the Air
This is the primary reason. Before modern air fresheners, people used aromatic herbs and spices to combat household odors (from cooking, illness, mustiness, etc.).
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Onions: Have natural antimicrobial and antibacterial properties. They were historically used in sickrooms to “absorb” germs and miasma (the old theory of bad air causing disease).
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Cloves: Are powerfully aromatic and also have strong antimicrobial and antiviral properties due to a compound called eugenol.
The combination was believed to create a potent “air-cleaning” duo. The strong scent would mask odors, and the antimicrobial properties would help purify the air, especially during cold and flu season.
2. As a Folk Remedy for Illness
It was common to place a clove-studded onion in a room where someone was sick (especially with a respiratory infection like a cold or flu). The belief was that it would:
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Draw out toxins and illness from the air and the person.
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Help clear congestion with its strong scent.
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Prevent other family members from getting sick.
Many people swear that the onion turns black or decays quickly in a sickroom, which they interpret as proof it “absorbed” the illness. (In reality, a cut onion exposed to air and bacteria will naturally discolor).
3. To Repel Insects
The strong smell of cloves and onions can act as a mild insect deterrent. This method was sometimes used in pantries or cupboards to keep moths and other pests away from foodstuffs.
4. A Kitchen Trick for Flavor
While less common for a whole onion, studding an onion with cloves is a classic technique in cooking (especially in stocks, broths, and stews) to add a warm, sweet, and aromatic depth of flavor. Your grandmother might have also been preparing a flavor base for soup.
The Science Behind the Folklore:
Modern science shows there’s some validity to the practice:
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Clove oil (eugenol) is a proven antimicrobial and is used in dentistry for its antiseptic properties.
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Onions contain sulfuric compounds and quercetin, which have some antibacterial effects.
While a single clove-studded onion won’t sterilize a room like a HEPA filter or UV light, it does release these compounds into the air, providing a mild antiseptic and deodorizing effect. The psychological benefit of a clean, spicy scent also shouldn’t be underestimated.
In short, your grandmother was using a time-honored, natural method to create a healthier, better-smelling home environment. It’s a beautiful example of practical, pre-industrial wisdom passed down through generations.