Onion (Allium cepa L.) is a 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 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.
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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.
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)
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.
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.
Hypertension (high blood pressure)
Onion-olive oil capsules may help lower blood pressure, although additional research is needed to make a firm recommendation.
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 strong recommendation.