Onion (Allium cepa)

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.

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.

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.
 
Allergies (Grade: 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.
Alopecia areata (hair loss) (Grade: 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.
Cancer (risk) (Grade: 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
Diabetes (Grade: 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.
Heart attack (risk) (Grade: C)
Early evidence suggests that consumption of onions and other vegetables belonging to the
High blood pressure (Grade: C)
Onion-olive oil capsules may help lower blood pressure, although additional research is needed to make a firm conclusion.
High cholesterol (Grade: 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.
Scar prevention (Grade: 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.