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Onion
🐾Zwiebel · (Allium cepa)
Amaryllis family (Amaryllidaceae)
Description
The layered, papery-skinned storage bulb of this amaryllis-family vegetable releases sulphur compounds on cutting that are responsible for its sharp smell and the well-known effect on the eyes. Harvested in summer, the bulb contains alliin and allicin, the flavonoid quercetin, and prebiotic inulin-type fructooligosaccharides. As a kitchen staple it appears in nearly every world cuisine and supplies notable amounts of vitamin C and potassium. Raw onion is traditionally regarded as a digestive and circulation-supporting home remedy, while onion decoction sweetened with honey is a long-standing remedy for cold-related cough. A warm onion poultice also features in folk medicine for earache and insect bites. WARNING: large amounts of raw onion can cause heartburn and flatulence; warm poultices on sensitive skin, especially in children, carry a risk of scalding.
Raw onion as spring tonic and digestive stimulant: promotes salivary and gastric secretion, mildly supports blood pressure regulation, traditionally regarded as a kitchen remedy for the circulation. Rich in quercetin and sulphur compounds.
Preparation & dosage
Onion cough tea or onion decoction for cold-related cough and hoarseness: a traditional home remedy reputed to be expectorant and mildly antibacterial. Honey adds soothing effect and improves the taste.
Preparation & dosage
Culinary staple used in nearly every cuisine: milder when cooked, sharper raw. Provides prebiotic fructooligosaccharides (inulin-type) for gut flora.
Preparation & dosage
Onion tincture (onion juice with honey, or alcohol macerate) as folk cough remedy and mild tonic. Traditionally used at the onset of colds.
Preparation & dosage
Onion poultice or warm onion compress as an old home remedy for earache, insect bites and painful swellings. The warm, chopped onion is wrapped in a cloth and placed on the affected area. NOT a substitute for medical evaluation of earache, especially in children.
Preparation & dosage
Freshly cut onion as bedside inhalation for blocked nose and cold: a halved onion on the night-stand is a folk remedy said to ease nocturnal breathing.
Preparation & dosage
Large amounts of raw onion can cause heartburn, flatulence and bad breath. Use cautiously with sensitive stomach, reflux or irritable bowel. Take care when applying warm onion poultices to sensitive skin, especially in children — risk of scalding. ASPCA classification (accessed 2026-08-10): toxic to dogs and cats.
Safe in normal culinary amounts. Larger medicinal doses (e.g. tincture) during pregnancy have not been systematically studied — use sparingly.
Unproblematic in culinary amounts; larger quantities can noticeably change the taste of breast milk and may promote gas in the infant.
Well tolerated as food from weaning age. Onion cough tea with honey only after the first birthday (botulism risk from honey). Warm onion poultices only hand-warm, never hot.
Drug interactions
Antikoagulanzien / Thrombozytenaggregationshemmer
Sulphur compounds in onion inhibit platelet aggregation; clinically irrelevant in culinary amounts, but very high intake or concentrated extracts may theoretically add to bleeding tendency.
Antidiabetika
Onion may mildly lower blood glucose; with high-dose regular intake alongside insulin or oral antidiabetics, an additive effect is theoretically possible — monitor blood glucose.
Contraindications
- Known Allium allergy (rare, may present as contact dermatitis or asthmatic reaction).
- Acute severe reflux oesophagitis or active gastric/duodenal ulcers — avoid raw onion.
- Do not feed to dogs, cats or other pets — Allium species are haemolytically toxic to them.
Harvested part: bulb (summer)
- Time of day:
- Harvest on a dry, sunny day once more than half of the foliage has bent over and yellowed.
- Drying:
- Lift bulbs carefully, cure for 2-3 weeks in an airy, dry, shaded place until the outer skins rustle. Only then remove foliage and roots.
- Storage:
- 6 months — Store cool (about 4-10 °C), dark, dry and airy, e.g. in nets, crates or braided plaits. Do not store together with potatoes.
- Time of day:
- Cut young leaf tubes in spring in the morning once the dew has dried — either from overwintered bulbs or from plants grown specifically as spring/scallion onions.
- Drying:
- Best used fresh; for preservation, finely chop and freeze. Drying is possible but strongly degrades aroma and sulphur compounds.
- Alliin / Allicin und verwandte Alk(en)yl-CysteinsulfoxideOtherContent: 0.5-1 % (frisch, je nach Sorte)use.plant_part.bulb
Sulphur-containing cysteine sulphoxides (mainly isoalliin, less alliin than in garlic). On cutting, the enzyme alliinase releases reactive thiosulphinates and the lachrymatory factor sulphine — responsible for smell, pungency and much of the pharmacology (antimicrobial, antiplatelet).
- Quercetin und Quercetin-Glykoside (v. a. Spiraeosid)FlavonoidContent: 0.03-0.1 % (Trockengewicht, in roten Sorten höher)use.plant_part.bulb
Main onion flavonoid; antioxidant, capillary-stabilising, anti-inflammatory in vitro. Red onions and the outer skins are especially rich in quercetin.
- Fructo-oligosaccharide (Inulin-Typ)PolysaccharideContent: ca. 5-10 % der Frischmasseuse.plant_part.bulb
Prebiotic storage carbohydrates (kestose, nystose and higher fructans). Promote bifidobacteria in the colon; may cause flatulence in sensitive individuals (FODMAP).
- Saponine (Spirostanol- und Furostanol-Typ)SaponinContent: Spuren bis < 0,5 %use.plant_part.bulb
Present only in small amounts, but contribute to antimicrobial and expectorant activity.
- Ätherisches Öl (schwefelhaltig)Essential oilContent: 0.005-0.015 %use.plant_part.bulb
Sulphur-containing volatile compounds (disulphides, trisulphides, thiosulphinates); characteristic of smell and taste. Yield is very low, so pure essential onion oil is rarely traded.
- Phenolcarbonsäuren (Kaffeesäure, Ferulasäure, p-Cumarsäure)Phenolic acidContent: Spurenuse.plant_part.bulb
Minor antioxidant accompanying compounds, especially in the skins.
- Vitamin C, B-Vitamine (Folat, B6)VitaminContent: ca. 7 mg Vitamin C / 100 g frischuse.plant_part.bulb
Contributes to the onion's historical role as a vitamin C winter vegetable, especially in storable form.
- Mineralstoffe (Kalium, Selen, Schwefel)MineralContent: ca. 150 mg Kalium / 100 guse.plant_part.bulb
Selenium is incorporated into the sulphur compounds and is considered a co-contributor to the antioxidant effect.
- [1]MonographKommission E Monographie: Allii cepae bulbus (Zwiebel)(accessed: 2026-05-19)
- [2]MonographPlants for a Future — Allium cepa(accessed: 2026-05-19)
- [3]MonographHeilkräuter-Lexikon: Zwiebel (Allium cepa)(accessed: 2026-05-19)
- [7]MonographASPCA Animal Poison Control — Onion (Allium cepa)(accessed: 2026-08-10)
- [8]MonographCliniTox Giftpflanzen — Allium cepa L.: stark giftig ++ (Institut für Veterinärpharmakologie und -toxikologie, Universität Zürich)(accessed: 2026-08-10)
- [4]WikipediaWikipedia (DE): Küchenzwiebel(accessed: 2026-05-19)
- [5]WikipediaWikipedia (EN): Onion (Allium cepa)(accessed: 2026-05-19)
- [6]WikidataWikidata: Allium cepa (Q81513)(accessed: 2026-05-19)
🤝 Permaculture Partners
In your garden, this plant acts as:
✨ Best symbiotic partners
- 🌿 Chives Both Allium family, coexist without issue.
- 🌿 Beetroot Classic companion-planting partner.
- 🌿 Kohlrabi Classic companion-planting partner.
- 🌿 Broccoli Onion deters cabbage root fly.
- 🌿 Cucumber Onion deters mildew spores from cucumbers.
- 🌿 Zucchini Classic companion-planting partner.
- 🌿 Carrot Carrot deters onion fly.
- 🌿 Lettuce Classic companion-planting partner.
- 🌿 Lettuce Classic companion-planting partner.
- 🌿 Matricaria chamomilla Chamomile boosts onion aroma — old farming rule.
- 🌿 Parsnip Classic companion-planting partner.
- 🌿 Parsley Classic companion-planting partner.
- 🌿 Tomato Classic companion-planting partner.
- 🌿 Spinach Classic companion-planting partner.
- 🌿 Tagetes patula Marigold deters onion fly.
⚠️ Better not planted together
- 🥬 Phaseolus vulgaris Onion and bean inhibit each other.
- 🥬 Phaseolus vulgaris Classic companion-planting partner.
- 🥬 Snap pea Classic companion-planting partner.
- 🥬 Pea Pea and onion should be separated — growth inhibition.
📦 Part of these planting sets:
Source: Helga und Margarete Langerhorst, Mein gesunder Naturgarten (eigene Kuration)