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What is Onion?

The onion plant is a perennial herb with hollow cylindrical leaves. On top of the long stalk are greenish-white flowers, and the seeds of the plant are black and angular. The underground bulb is used both medicinally and as a food.

Scientific Name(s)

Allium cepa L.

Common Name(s)

Onion, Bulbus Allii Cepae, common onion, garden onion. Topical commercial preparations include Contractubex and Mederma.

Trade Names

  • Contractubex
  • Mederma

What is it used for?

Traditional/Ethnobotanical uses

Central and western Asia is believed to be the region where onions were domesticated. Onions were pictured as early as 5,000 years ago on ancient Egyptian monuments. Ancient Greek and Roman writings also refer to the onion. During the Middle Ages, onions were consumed throughout Europe. They later were thought to guard against evil spirits and the plague, probably because of their strong odor. Onion skin dye has been used for egg and cloth coloring for many years in the Middle East and Europe. Columbus was said to have brought the onion to America. Folk healers used the onion to prevent infection. The combination of onions and garlic cooked in milk is a European folk remedy used to clear congestion. Onion has potential in treating heart disease, hyperglycemia, and stomach cancer, although few quality clinical trials are available to support these uses. Topical preparations have been evaluated to prevent surgical scarring with varying success.

What is the recommended dosage?

Clinical trials are lacking to provide dosage recommendations. Average daily doses of 50 g of fresh onion, 50 g of fresh onion juice, or 20 g of dried onion have been suggested. Topical onion extract gels have been used in studies evaluating the effect on scarring and are generally applied 3 times daily.


Contraindications have not yet been identified.


Generally recognized as safe when used as food. Avoid dosages above those found in foods because safety and efficacy are unproven.


None well documented.

Side Effects

Few reported.


Information is limited.


1. Onion. Review of Natural Products. Facts & Comparisons [database online]. St. Louis, MO: Wolters Kluwer Health Inc; October 2010.

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