Updated: Sep 2, 2019
Authored by: Kristina Iman Renkhoff - Ibn Sina GIHM Student
Being used in everyday’s kitchen, in almost every country of the world, one would not commonly suspect that there might be more to onions, other than flavoring dishes. Nevertheless, in 2015, Allium cepa, the common onion, has been elected “Healing plant of the year”, a prize awarded by the herbal association NHV Theoprastus in Germany. Reason enough, to take a closer look.
Appearance and origin
The common onion belongs to the Liliaceae family and is an annual or perennial plant, up to 100 cm tall, has hollow stems and leaves and white or purple flowers. The real stem is very short, formed at the base of the plant in the form of a disk, with adventitious roots at base. The bulb is formed by the thickening of leaf-bases, solitary or in clusters. The bulb varies in shape from depressed globose to ovoid or oblate, can be up to 20 cm in diameter, and is usually colored white or red. The part used for its medicinal properties is the bulb.
The common onion is only known from cultivation. It probably originates from Central Asia (between Turkmenistan and Afghanistan), where some of its relatives still grow in the wild. From there, the supposed onion ancestor probably migrated first towards Mesopotamia, where onion is mentioned in Sumerian literature (2500 BC), then to Egypt (1600 BC), India and South-East Asia. From Egypt, Allium cepa was introduced into the Mediterranean area and from there to all the Roman Empire.
Onions can grow on any soil with pH above 5.6, but adequate calcium nutrition is essential for good vegetative development and disease tolerance.
Onions can be either grown by plug onions or by seeds. The main difference is, that cultivation time is longer, if grown from and that seeds and can be planted earlier in the year. Plugs, as they contain water, should not be planted in those months when the ground may still be frosted.
Cultivated in the northern hemisphere, onions require little maintenance. They do not require a lot of water, weed should be regularly extracted and the soil loosened from time to time. A mixed planting with carrots is beneficial for both plants to reduce pests.
For immediate consumption, onions may be harvested from early summer on. If storage is intended though, they can be harvested as soon as the onion leaves are getting dry and are starting to bend. Then, the bulb simply has to be extracted from the soil and left to dry in dry weather conditions for a few days, during which it is turned regularly. Due to this process, the outer layers are drying and the bulb is getting storable.
Onions should be stored in a dark, cool and dry place, so they can be kept many weeks. They should not be stored next to potatoes, as they soke up water from the potatoes and might go off sooner, in return, the potatoes might dry and start sprouting easier.
In popular medicine, onion is used to relief cold symptoms such as cough, stuffed nose, sore throat or even bronchitis. Externally applied, onion reliefs ear pain and soothes insect bites.
To relief cough or stuffed nose, it is sufficient to cut an onion into small pieces and put it on a plate next to the patient. This is particularly handy with smaller children, since compliance is not an issue. Nevertheless it has a strong effect, even in adults.
To produce a cough syrup, onions can be cut into small pieces and be mixed with either honey or brown sugar and left overnight. The syrup can be taken repeatedly if needed.
An infusion made with freshly cut onions is also beneficial for cough or other cold symptoms.
To relief earache, the onion pieces should be warmed to body temperature, e.g. in an oven or steamer, put in a cotton cloth and then be placed on the ear. For insect bites, it suffices to cut an onion in halves and place the section on the bite.
Modern Medicine Uses
Onion boasts a long list of medicinal actions – diuretic, antibiotic, anti-inflammatory, analgesic, expectorant, and anti-rheumatic. It is also beneficial to the circulation. Onions are taken the world over for colds, flu and coughs, much like garlic (Allium sativum). Onion offsets tendencies to angina, arteriosclerosis, and heart attack. It is also useful in preventing oral infection and tooth decay. The warmed juice can be dropped into the ear for earache, and baked onion is used as a poultice to drain pus from sores. Onion has a long standing reputation as an aphrodisiac, and it is also used cosmetically to stimulate hair growth.
In in-vitro experiments onion showed antibacterial and antifungal activity against both gram-positive and gram-negative bacteria (including enteropathogens), pathogenic yeast (Candida spp.) and some skin-pathogenic fungi. Onion juice has been shown to have anti-hyperglycaemic and anti-asthmatic properties. The best investigated medicinal activity, however, is the effect on platelet aggregation. Onion extracts have shown in-vitro activity against platelet aggregation, but clinical tests have shown conflicting or inconsistent results. Regular consumption of onion has been reported to reduce the risk of stomach cancer.
In homeopathy, Allium cepa is also used for cold symptoms that originate from wet and cold weather conditions. Rhinitis with skin-irritating secretion, sinusitis, pollinosis, watering eye and photophobia can also be treated with Allium cepa. Another indication would be foul-smelling flatulence.
Per definition, the difference between food and medicine is that food is defined as something that nurtures the body and causes growth or replacement, whereas medicine is defined as something that changes the “mizage” (temperament).
In his poem, the Urjoozah fi at-Tibb, Ibn Sina includes onions in the food category, but at the same time he says that (along with garlic and mustard) they “produce yellow bile and might be taken as medicine” in the appropriate condition. Therefore onion takes a stand in between food and medicine.
For internal use, onion may be administered raw or gently cooked. Ibn Nafīs classifies onion as hot 3rd degree and dry 2nd degree. Its properties are “muhalim” – pain reliefing, “muqatta” – crushing solid substances, “jaalin” – separating sticky liquids, “mufattih” – opening the passages - and “muhammir” – bringing blood to the surface of the skin.
If applied externally, onion with salt destroys flesh that grows on the surface of the skin. Onion seed is used to get rid of white, brown or black patches of the skin. Taken internally, it strengthens the stomach, arouses desire of food, makes a person feel thirsty, excites for the sexual act and increases sexual strength and releases the monthly cycle.
Possible adverse effects
According to Ibn Nafīs, consuming big amounts of onion may harm the brain, as well as cause headache and make the consumer sleepy. In patients with hot and dry constituencies, onion should be applied carefully, as it has the same properties. A common noted side effect, when eaten, is bloating, but may differ from person to person and depending on the onion subtype. Rarely, onion can irritate the mucous membrane of the intestinal tract.
Summarizing the above, as humble and as ordinary the common onion might appear at first sight, it becomes clear that the title “Healing plant of the year 2015” is well deserved. Onion is a beneficial healing plant and especially in the flu season, an absolute must-have herb.
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