Origin: Onions have been cultivated for over 7000 years now. They grow up to a height of 15 to 45 cms. They have yellow/bluish-green leaves and are flat with fan shape and the roots are fibrous. Once the leaves die back and the outer becomes dry and brittle, it means it’s ready to be harvested. The average PH balance of onion is 5.5. Onions are one of the easiest and earliest cultivated crops. Onions can grow in any soil and climate and are easily transported. 
It is believed that onions originated in central Asia and they were first grown in Iran and West Pakistan. Onions also find their traces in ancient books and are believed that they grew Chinese gardens 5000 years ago.   Onions are also mentioned in old Vedic writings in India.  In Egypt, onions can be traced back to 3500 B.C.
In Egypt, onions were considered to be an object of worship and were scared to them. The onion symbolized eternity to the Egyptians who buried onions along with their Pharaohs. They believed that onions gave better afterlife.  The Egyptians believed in eternal life in the anatomy of the onion because of its circle-within-a-circle structure. You can also spot paintings of onions on the inner walls of the pyramids and in the tombs of both the Old Kingdom and the New Kingdom. The onion is also mentioned as a funeral offering and depicted on the banquet tables of the great feasts – both large, peeled onions and slender, immature ones. They were presented as an offering to the altars of the gods. 

In the 6th century B.C, Indians believed that the onions are a medicine. It works wonder ad a diuretic, helps in digestion, the heart, the eyes, and the joints.

Scientifically: Onions belong to the allium family of vegetables. They are into the same group as garlic, chives, leek, and scallions. Onions are also known as the Bulb onion or common onion. 
Onions are scientifically called Allium. It is a biennial or perennial plant. It is annually harvested and cultivated all over the world. This is used for cooking and is a part of savory dishes. It can also be eaten raw or in salads. They are pungent and release a substance which irritates the eyes while chopping. 

Usage: Onions are low in calorie and are full of vitamins and minerals. It contains a high amount of vitamin C which helps in boosting immunity, increases collagen production and repairs skin tissue.
Onions are full of antioxidants which help in treating inflammations. Onions also help in lowering cholesterol levels. Onions also improve bone density.     Onions are known for their antibacterial properties and help in keeping acne at bay. Onion is a great source of flavonoids as well as antioxidant vitamins, such as Vitamin A, vitamin C, and vitamin E. All these help in protecting our skin cells from the damaging effects of ultraviolet (UV) rays.

Below are some DIYs with onions for beautiful skin and hair:

-    Take a medium-sized onion and cut it into small pieces and extract the juice. Dip a cotton ball into it and apply all over your skin. This mask helps in achieving wrinkle-free, firmer and young-looking skin with a better texture.
-    Take one tablespoon of onion juice and add one tablespoon of olive oil or almond oil to it. Blend well and apply on your skin. After 15 minutes, wash off with cold water. This helps in removing acne.
-    Take a tablespoon of fresh onion juice with one tablespoon of plain yogurt. Add 4 to 5 drops of lavender oil to the mixture. Massage your face with it in a gentle circular motion by using your fingertips. This helps in reducing pigmentation.
-    Take equal amounts of lemon juice and onion juice. Mix them together and Dab it on your skin with a cotton ball. Wash away with lukewarm water after 10 to 15 minutes. This helps in removing acne scars.
-    Take 3 tablespoons of onion juice and add half a teaspoon of turmeric powder to it. Mix well and apply on irritated skin areas on the body. This helps in soothing the skin.
-    Take one medium-sized onion juice and extract its juice. Apply this juice to your hair roots and leave it on for 30 minutes. Rinse it with mild shampoo later. This remedy helps in promoting hair growth.