Onion

Related Terms

Allicepin, allicin, alliin, Allium cepa, Allium cepa L., allium vegetables, allylsulfides, apigenin, anthocyanins, botanicals, caffeic acid, cinnamic acids, cycloalliin, cysteine, diallyl disulfide, dipropyl disulfide, green onion, isoquercetin, isorhamnetin, kaempferol, L-cysteine sulfoxide, lignans, Liliaceae (family), luteolin, myricetin, onion extract, onion juice, onion powder, onion vinegar, organosulfur compounds, p-hydroxybenzoic acid, phytoestrogens, pickling onions, protocatechuic acid, quercetin, quercetin diglucoside, quercetin monoglucoside, red onion, rutin, S-alk(en)yl cysteine sulfoxides, S-allylcysteine, selenium, Spring Sweet, Sweet Imperial, syn-propanethial-S-oxide, taxifolin, Texas Grano 438, thiosulfinates (allyl methyl trisulfide, diallyl sulfide), Ultra Hybrid, vanillic acid, Vidalia onions, Walla Walla, white onion.
Note: Onion (Allium cepa) should not be confused with plants of the Zigadenus species.

Background

Onion (Allium cepa L.) is widely used around the world as a food product and has also been used for medicinal applications.
Most of the available research has focused on scar prevention, but the results are mixed in this area. Onion has been used in the treatment of diabetes, cancer, heart disease, and alopecia areata (hair loss).
As onion is a commonly consumed food, it is considered likely safe in smaller amounts, although there are reports of skin rash and gastrointestinal problems in sensitive individuals.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Early study suggests that application of an alcoholic onion extract on the skin may reduce allergic responses, such as wheals ("hives") and flares. More research is needed in this area.

 C


Early study suggests that application of an alcoholic onion extract on the skin may reduce allergic responses, such as wheals ("hives") and flares. More research is needed in this area.

 C


Study using topical onion juice increased hair regrowth in alopecia areata (hair loss) patients, especially women. More research is needed in this area to confirm these results.

 C


Study using topical onion juice increased hair regrowth in alopecia areata (hair loss) patients, especially women. More research is needed in this area to confirm these results.

 C


Early evidence suggests that onion or onion extract prevents cancer, including gastrointestinal, ovarian, skin, and endometrial cancers. Some studies, however, have reported no association between Allium vegetable consumption and incidence of cancer (particularly breast and lung cancer). More research is needed before a conclusion can be made.

 C


Early evidence suggests that onion or onion extract prevents cancer, including gastrointestinal, ovarian, skin, and endometrial cancers. Some studies, however, have reported no association between Allium vegetable consumption and incidence of cancer (particularly breast and lung cancer). More research is needed before a conclusion can be made.

 C


One clinical trial found that fresh onion significantly decreased serum glucose (blood sugar) levels in diabetics. More research is needed in this area to confirm these results.

 C


One clinical trial found that fresh onion significantly decreased serum glucose (blood sugar) levels in diabetics. More research is needed in this area to confirm these results.

 C


Early evidence suggests that consumption of onions and other vegetables belonging to the Allium genus may reduce the risk of heart attack. More well designed studies are needed before a conclusion can be made.

 C


Early evidence suggests that consumption of onions and other vegetables belonging to the Allium genus may reduce the risk of heart attack. More well designed studies are needed before a conclusion can be made.

 C


Onion-olive oil capsules may help lower blood pressure, although additional research is needed to make a firm conclusion.

C


Onion-olive oil capsules may help lower blood pressure, although additional research is needed to make a firm conclusion.

C


Research in humans found that onion may have an effect on blood serum triglyceride, betalipoprotein cholesterol and phospholipid levels. More research is needed in this area to confirm these results.

 C


Research in humans found that onion may have an effect on blood serum triglyceride, betalipoprotein cholesterol and phospholipid levels. More research is needed in this area to confirm these results.

 C


Several trials have been conducted using combination products that include an onion extract. These studies have investigated onion's potential role in scar healing in adults and children, specifically due to injuries from laser tattoo removal or surgery. The overall results are mixed, and more research is needed to make a conclusion.

 C


Several trials have been conducted using combination products that include an onion extract. These studies have investigated onion's potential role in scar healing in adults and children, specifically due to injuries from laser tattoo removal or surgery. The overall results are mixed, and more research is needed to make a conclusion.

 C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (over 18 years old)
There is currently no proven effective medicinal dose of onion in adults.
For diabetes, a diet supplemented with 20 grams of fresh onion three times daily has been taken by mouth.
For high blood pressure, four onion-olive oil maceration capsules have been taken by mouth daily for one week.
For scars, the following has been used: Mederma? (Merz Pharmaceuticals, Greensboro, NC, USA) applied to the skin three times daily for eight weeks; an onion gel extract applied to the skin three times daily for one month or for 10 weeks; Contractubex? gel (10% onion extract, 50IU of sodium heparin per gram of gel, and 1% allantoin) rubbed into scars 1-4 times daily for up to six months.
For alopecia areata, Australian brown onion juice has been applied to areas of hair loss twice daily for two months.
For determination of allergies, onion juice solution in 45% ethanol has been injected into the skin followed by an undiluted onion solution being applied to the skin at the injection sites.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
Cepae extract from onions, heparin, and allantoin may improve healing of injuries incurred during laser tattoo removal or surgery.
Meals including onion have induced heartburn, dyspepsia (upset stomach), gastric acidity, and gastroesophageal reflux in clinical trials. Use onion cautiously with antacids.
Allium plants, such as onion, may have antibiotic effects, and may have additive effects when used with other antibiotics.
Onion may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin?) or heparin, anti-platelet drugs such as clopidogrel (Plavix?), and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen (Motrin?, Advil?) or naproxen (Naprosyn?, Aleve?).
Onion may lower blood sugar. Caution is advised in patients with diabetes (high blood sugar) or hypoglycemia (low blood sugar), and in those taking drugs that affect blood sugar. Serum glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.
Onion and onion essential oil may prevent fat-induced increases in serum cholesterol. Use cautiously with cholesterol-lowering medications.
Onion or onion extract may have anticancer effects. Use cautiously when taken with medications to prevent or treat cancer.
Onion may lower blood pressure; use cautiously with blood pressure medications.
Onion may inhibit bone resorption; use cautiously with osteoporosis agents.
Onion may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be increased or decreased in the blood, and may cause increased or decreased effects or potentially serious adverse reactions. Patients using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Onion may also interact with allopurinol, antidepressants, antifungals, anti-inflammatory agents, hormonal agents, nicotine, p-glycoprotein-regulated agents, simvastatin, triamcinolone, and uridine diphasophate glucuronosyl transferase substrates.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

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