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Herbal Medicine

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Latin Name: Allium cepa

Pharmacopeial Name: Allii cepae bulbus

Other Names: n/a



•Chemistry and Pharmacology



•Side Effects

•Use During Pregnancy and Lactation

•Interactions with Other Drugs

•Dosage and Administration


•Additional Resources


Onion is a bulbous perennial or biennial herb believed to be native to western Asia. Numerous varieties are cultivated worldwide (Leung and Foster, 1996). It is cultivated throughout India (Kapoor, 1990). Some sources state that it is native to Hungary (Felter and Lloyd, 1985; HPUS, 1992).

Onion bulb has been used as a food for thousands of years. It has also been used medicinally. According to traditional European herbalists, onions are antiseptic and diuretic in action (Grieve, 1979). They are used therapeutically in the Ayurvedic, Siddha, and Unani systems of Indian medicine, in various dosage forms including the decoction, infusion, and fresh juice, as well as raw, cooked, and/or roasted bulb. The juice form is usually combined with honey, ginger rhizome juice, and ghee (liquid clarified butter) (Nadkarni, 1976). Its introduction into traditional Chinese medicine is fairly recent and its use limited (Leung and Foster, 1996). The official onion bulb of the Pharmacopoeia of the People’s Republic of China is a different species (Allium macrostemon Bge.) than that of the Commission E monographs (A. cepa). The Chinese pharmacopeia indicates its use for treatment of angina pectoris, cough, and dyspnea (painful, difficult breathing), and also tenesmus (painful spasmodic contraction of anal or vesical sphincter) in dysentery (Tu, 1992).

In Germany, onion bulb is approved in the Commission E monographs for loss of appetite and prevention of atherosclerosis. The World Health Organization supports Commission E, noting that the following use is supported by clinical data: ‘treatment of age-dependent changes in the blood vessels, and loss of appetite’ (WHO, 1999). Onions are also cooked in milk and eaten in order to clear congestion in the lungs (Shultz et al., 1998). In the United States, onion bulb was used somewhat in the Eclectic system of medicine during the nineteenth century and early twentieth century. Its actions were considered to be comparable to those of garlic, though milder. It was dispensed as a syrup, made from the fresh juice with sugar, for treatment of cough and bronchial conditions. It was also given as a tincture, made with gin, for kidney gravel and/or dropsy (Felter and Lloyd, 1985). Onion is presently classified in the Homeopathic Pharmacopoeia of the United States as an OTC Class C drug prepared as a 1:10 (w/v) alcoholic tincture of the mature bulb (preferably the red variety), in 45% v/v alcohol (HPUS, 1992).

Several clinical studies have been found in the literature. Recent investigations suggest that therapies aimed toward the prevention of atherosclerosis should include a diet rich with onions. Contemporary studies have shown that onions, like garlic, may inhibit platelet aggregation and interfere with fibrinolyis (Leung and Foster, 1996; Reynolds, 1989). The antiplatelet activity is genotype dependent and correlates directly with bulb sulfur content (Goldman et al., 1996). Antihypercholesterolemic and hypoglycemic uses for onions have also been supported by research. Clinical studies have reported that onions lowered lipid levels and inhibited the formation of blood clots in study subjects (Schulz et al., 1998). Other studies have investigated the effect of butter fat and onion on coagulability of blood (Jain, 1971), its effects on serum triglyceride, betalipoprotein-cholesterol, and phospholipids in alimentary lipemia (Jain et al., 1973), the fibrinolytic activator action of steam-distilled and ether extract of onion (Augusti et al., 1975), the effects of an oily chloroform extract of onion on platelet aggregation and thromboxane synthesis (Makheja et al., 1979), the effects of an aqueous extract of onion on the inhibition of platelet aggregation (Srivastava, 1984), the use of crude onion oil in the treatment of hypertension and hyperlipidemia (Louria et al., 1985), and the relationship between consumption of onions with a reduced risk of stomach carcinoma (Dorant et al., 1996; You, 1988; You et al., 1989).

A pharmacopeial grade onion bulb has not been defined at present.


Onion consists of the fresh or dried, thick and fleshy leaf sheaths and stipules of Allium cepa L. [Fam. Alliaceae] and their preparations in effective dosage. It contains alliin and similar sulfur compounds, essential oil, peptides, and flavonoids.

Chemistry and Pharmacology

Onion bulb contains numerous organic sulfur compounds, including trans-S-(1-propenyl) cysteine sulfoxide, S-methyl-cysteine sulfoxide, S-propylcysteine sulfoxide, and cycloalliin; flavonoids; phenolic acids; sterols including cholesterol, stigmasterol, b-sitosterol; saponins; sugars; and a trace of volatile oil composed mainly of sulfur compounds, including dipropyl disulfide (Kapoor, 1990; Leung and Foster, 1996). A fresh onion bulb contains fructans with a low degree of polymerization, flavonoids, and sulfur-containing compounds. When an onion bulb is bruised, the sulfoxides are degraded by alliinase and release pyruvic acid and alkylthiosulfinates, which rapidly form into disulfides (Bruneton, 1995).

The Commission E reported antibacterial, lipid, and blood pressure-lowering properties and inhibition of thrombocyte aggregation.

Onions have appetizer and gastric tract stimulant actions (Taber, 1962). An animal study concluded that serum, liver, and aorta triglyceride levels were decreased after use of an aqueous extract of onion (Sebastian et al., 1979). In vitrostudies have shown antimicrobial activity and animal studies have demonstrated hypoglycemic activity (Bruneton, 1995). The antibacterial activity of onion was determined by a study that researched the activity of oral bacteria, including Streptococcus mutans and Porphyromonas gingivalis (Kim, 1997).


The Commission E approved onion for loss of appetite and prevention of atherosclerosis.

Supporting the Commission E uses, the World Health Organization notes the following uses are supported by clinical data: age related change in blood vessels and loss of appetite (WHO, 1999).

A preliminary epidemiological study suggests that increased consumption of onion, as well as other Allium vegetables, may reduce the risk of gastric cancer (You et al., 1989).


None known.

Side Effects

None known.

Use During Pregnancy and Lactation

No restrictions known.

Interactions with Other Drugs

None known.

Dosage and Administration

Unless otherwise prescribed: 50 g per day of fresh bulb or 20 g per day of cut dried bulb, pressed juice from fresh onions and other oral galenical preparations.

Dried bulb: 20 g (Commission E).

Fresh bulb: 50 g (Commission E).

Infusion: Steep 1-2 teaspoons in 120 ml water (Lust, 1974).

Succus: 5 ml (1 teaspoon) pressed juice of fresh bulb, three to four times daily (Lust, 1974).

Tincture: 5 ml (1 teaspoon), three to four times daily (Fleming et al., 1998).

Duration of administration: Note: If onion preparations are used over several months, the daily maximum amount for diphenylamine is 0.035 g.


Augusti, K.T., M.E. Benaim, H.A. Dewar, R. Virden. 1975. Partial identification of the fibrinolytic activators in onion. Atherosclerosis 21(3):409416.

Bruneton, J. 1995. Pharmacognosy, Phytochemistry, Medicinal Plants. Paris: Lavoisier Publishing.

Dorant, E., P.A. van den Brandt, R.A. Goldbohm, F. Sturmans. 1996. Consumption of onions and a reduced risk of stomach carcinoma. Gastroenterology 110(1):1220.

Felter, H.W. and J.U. Lloyd. 1985. King’s American Dispensatory, Vols. 12. Portland, OR: Eclectic Medical Publications [reprint of 1898 original]. 146.

Fleming, T. (ed.). 1998. PDR for Herbal Medicines. Montvale, N.J.: Medical Economics Company, Inc.

Goldman, I.L. M. Kopelberg, J.E. Debaene, B.S. Schwartz. 1996. Antiplatelet activity in onion (Allium cepa) is sulfur dependent. Thromb Haemost 76(3):450452.

Grieve, M. 1979. A Modern Herbal. New York: Dover Publications, Inc.

The Homeopathic Pharmacopoeia of the United States (HPUS) Revision Service Official Compendium. 1992. Fairfax, VA: Pharmacopoeia Convention of the American Institute of Homeopathy.

Jain, R.C. 1971. Effect of butter fat and onion on coagulability of blood. Indian J Med Sci 25(9):598600.

Jain, R.C., K.N. Sachdev, S.S. Kaushal. 1973. Effect of onion ingestion on serum triglyceride, betalipoprotein-cholesterol and phospholipids in alimentary lipaemia. J Assoc Physicians India 21(4):357360.

Kapoor, L.D. 1990. Handbook of Ayurvedic Medicinal Plants. Boca Raton: CRC Press. 25.

Kim, J.H. 1997. Anti-bacterial action of onion (Allium cepa L.) extracts against oral pathogenic bacteria. J Nihon Univ Sch Dent 39(3):136141.

Leung, A.Y. and S. Foster. 1996. Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics, 2nd ed. New York: John Wiley & Sons, Inc.

Louria, D.B. et al. 1985. Onion extract in treatment of hypertension and hyperlipidemia: A preliminary communication. Curr Ther Res 37(1):127131.

Lust, J. 1974. The Herb Book. New York: Bantam Books. 298.

Makheja, A.N., J.Y. Vanderhoek, J.M. Bailey. 1979. Effects of onion (Allium cepa) extract on platelet aggregation and thromboxane synthesis. Prostaglandins Med 2(6):413424.

Nadkarni, K.M. 1976. Indian Materia Medica. Bombay: Popular Prakashan. 6364.

Reynolds, J.E.F. (ed.). 1989. Martindale: The Extra Pharmacopoeia, 29th ed. London: The Pharmaceutical Press. 1597.

Schulz, V., R. Hnsel, V.E. Tyler. 1998. Rational Phytotherapy: A Physicians’ Guide to Herbal Medicine. New York: Springer.

Sebastian, K.L., N.T. Zacharias, B. Philip, K.T. Augusti. 1979. The hypolipidemic effect of onion (Allium cepa Linn) in sucrose fed rabbits. Indian J Physiol Pharmacol 23(1):2730.

Srivastava, K.C. 1984. Aqueous extracts of onion, garlic and ginger inhibit platelet aggregation and alter arachidonic acid metabolism. Biomed Biochim Acta 43(89):S335S346.

Taber, C.W. 1962. Taber’s Cyclopedic Medical Dictionary, 9th ed. Philadelphia: F.A. Davis Company. O9.

Tu, G. (ed.). 1992. Pharmacopoeia of the People’s Republic of China (English Edition 1992). Beijing: Guangdong Science and Technology Press. 8.

World Health Organization (WHO). 1999. ‘Allii cepae bulbus.’ WHO Monographs on Selected Medicinal Plants, Vol. 1. Geneva: World Health Organization. 515.

You, W.C. et al. 1989. Allium vegetables and reduced risk of stomach cancer. J Natl Cancer Inst 81(2):162164.

You, W.C. 1988. [A study on the relationship between consumption of Allium vegetables and gastric cancer] [In Chinese]. Chung Hua Yu Fang I Hsueh Tsa Chih 22(6):321323.

Additional Resources

Augusti, K.T. 1996. Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.). Indian J Exp Biol 34(7):634640.

Duke, J.A. 1997. The Green Pharmacy. Emmaus, PA: Rodale Press. 243, 245, 254255, 259.

Navarro, J.A. et al. 1995. Allium cepa seeds: a new occupational allergen. J Allergy Clin Immunol 96(5 Pt 1):690693.

Zohri, A.N., K. Abdel-Gawad, S. Saber. 1995. Antibacterial, antidermatophytic and antitoxigenic activities of onion (Allium cepa L.) oil. Microbiol Res 150(2):167172.

This material was adapted from The Complete German Commission E MonographsTherapeutic Guide to Herbal Medicines. M. Blumenthal, W.R. Busse, A. Goldberg, J. Gruenwald, T. Hall, C.W. Riggins, R.S. Rister (eds.) S. Klein and R.S. Rister (trans.). 1998. Austin: American Botanical Council; Boston: Integrative Medicine Communications.

1) The Overview section is new information.

2) Description, Chemistry and Pharmacology, Uses, Contraindications, Side Effects, Interactions with Other Drugs, and Dosage sections have been drawn from the original work. Additional information has been added in some or all of these sections, as noted with references.

3) The dosage for equivalent preparations (tea infusion, fluidextract, and tincture) have been provided based on the following example:

•Unless otherwise prescribed: 2 g per day of [powdered, crushed, cut or whole] [plant part]

•Infusion: 2 g in 150 ml of water

•Fluidextract 1:1 (g/ml): 2 ml

•Tincture 1:5 (g/ml): 10 ml

4) The References and Additional Resources sections are new sections. Additional Resources are not cited in the monograph but are included for research purposes.

This monograph, published by the Commission E in 1994, was modified based on new scientific research. It contains more extensive pharmacological and therapeutic information taken directly from the Commission E.

Excerpt from Herbal Medicine: Expanded Commission E Monographs

Copyright 2000 American Botanical Council

Published by Integrative Medicine Communications

Available from the American Botanical Council.


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