Onion has been used for over 5,000 years for both its versatile flavor and medicinal benefits. This vegetable has compounds that work as a natural antibiotic.

Quick Facts
General Information
  • Common name(s)Onion, bulb onion, common onion
  • Scientific nameAllium cepa
  • Native regionSouthern Europe
  • Main producer(s)China
  • Main Economic UseFood industry, Culinary

Onion, a vegetable originally from the Eastern Mediterranean, has been one of the most popular culinary additions around the world. Ancient Egypt was reportedly the first civilization to domesticate onion approximately 5,000 years ago. Documentation reveals that the onion was worshiped for its spherical shape and was considered a symbol of fertility. Experts also believe that onions were used for paying construction workers.

In ancient Greece, onions were consumed for their medicinal benefits, as they were thought to "lighten" the balance of blood. Roman gladiators also used onions to enhance muscle firmness. Widely regarded as a staple food during the Middle Ages, the bulbs were used to pay house rent. Nowadays, this essential is found in cupboards and cuisines across the globe.

Medicinal and Nutritional Information

Quick Facts (Medicinal and Nutritional Information)
  • Medicinal actionAnti-inflammatory, Antioxidant
  • Key constituentsAllicin, phenols, flavonoids
  • Ways to useCapsules, Ointment
  • Medicinal rating(2) Minorly useful plant
  • Safety rankingSafe
Onion Benefits

Health Benefits of Onion

Thanks to its rich nutritional value, onion works as a natural antibiotic and antioxidant.The medicinal properties of onions have been used in many ways throughout human history, such as:

  • Strengthening immunity

  • Treating respiratory tract infections

  • Reducing LDL cholesterol levels

How It Works

The main active ingredient behind onion's medicinal benefits is allicin, a sulfuric compound that's abundant across the Allium genus. Other phytocompounds found in onions include phenols and flavonoids - especially yellow onions - as well as quercetin and alliinases. The latter are mostly known for being the precursors to onion's lachrymatory factor (LF). Finally, onions contain vitamins C (ascorbic acid), B6 (pyridoxine), and B9 (folic acid).

Allicin inhibits RNA synthesis and hinders the reproduction of viruses and bacteria. Furthermore, phenols and quercetin possess antioxidant properties, inhibiting the cellular damage caused by free radicals.

The main active ingredient behind onion's uses is allicin, a potent antibacterial and antiseptic agent.

Onion Side Effects

However, onions also carry an unpleasant side effect of irritating the eyes and triggering inflammation of the tear glands. Typically, this occurs when chopping the vegetable, because aliinases are released when the onion's cells are damaged, and they begin to break down sulfoxides, generating different sulfenic acids. As a byproduct of this reaction, a volatile gas known as lachrymatory factor is created.

Diabetics should also be wary when consuming onion because it can potentially lower blood sugar levels to the point of resulting in hypoglycemia. Women who are pregnant and breast-feeding don't need to specifically avoid onion, but it should not be consumed in large amounts.

How to Consume Onion

Quick Facts (How to Consume)
  • Edible usesFlavoring, Condiment, Beverage, Oil
  • TastePungent

Onion bulbs in particular are highly regarded by both chefs and traditional regional cooks alike as a flavor enhancer for salads, sandwiches, stews, and many other types of preparations. The flavor added by onion is very popular and considered pleasing by most people, which has allowed its use to expand rapidly throughout the world and to influence different culinary styles.

Despite onion's pungent taste when raw, there are many ways to enjoy the plant's benefits


Quick Facts (Buying)
  • Where to buySupermarkets, Big online retailers, Farmers' markets, Specialized health stores, Online herb stores

Raw and Simply Processed Onion

Raw onion is easy to find in most grocery stores or local markets throughout the year. The most common presentation of raw onion includes the whole unpeeled bulbs, which can then be peeled and chopped to be eaten raw or cooked, depending on individual preference. Powdered, dehydrated onion can also be found, but it is much rarer and usually contained to specialized stores.

Onion Supplements

Onion supplements are mainly found in specialized health stores. In addition, there is a wide variety of onion supplement choices available through online retailers. Each brand of onion supplement may come with different concentrations and be presented in pill, capsule, or topical cream form.


Quick Facts (Growing)
  • Life cycleAnnual
  • Harvested partsRhizome
  • Growing habitatTemperate climates

Onions are best grown in similar conditions as garlic and other members of the Allium genus.

Growing Guidelines

  • Onions need sufficient exposure to cold temperatures in order to enhance the bulb's pungency and its antibiotic properties.

  • Onions should be grown from seeds, planted in rows, and should be germinated at 45 - 95°F (7 - 35°C).

  • Drip irrigation is the most appropriate system for growing onions, and they require replanting every year.

Additional Information

Plant Biology

Onion is an annual bulbous herb that is now grown extensively around the world, mainly for culinary purposes. The fleshy bulb is formed by dense layers of leaf bases, which contain the nutrients responsible for the onion's medicinal benefits.

  • Classification

    Onion is a member of the Amaryllidaceae family. This family contains herbaceous, bulbous flowering plants, including approximately 1,600 species. Onion is also a member of the subfamily Allioideae, which is characterized by its production of allyl sulfide, a compound that gives members of this subfamily, like onions or garlic, their characteristic smell, which is also related to their medicinal and culinary properties.

  • Varieties and Subspecies of Onion

    Over the course of history, different varieties and subspecies of onion have been cultivated through selective breeding in different regions of the world. The most common varieties are part of the common onion group. Plants in this group form large, single bulbs. There are also several European onions, which have protected geographical status.

Economic Data

Onions are mostly valued for alimentary and culinary purposes. Over 9 million acres of onions are grown throughout the world annually. They are now grown by 170 different countries for domestic use, and about 8% of onions are traded internationally. China is currently the world's largest producer of onions, harvesting over 20 million tons each year. India and the United States take second and third position.

Other Uses

Onion bulbs and raw onion have additional uses. Onion juice can be rubbed onto a fresh bee sting to ease the pain. To rid a house of that fresh paint smell, place a few slices of cut up onion into a bowl of water. Onion can also remove rust from kitchen utensils by rubbing them against an onion cut in half a few times.