Onion has a strong spicy aroma that can pervade your kitchen. Because of the wonderful flavor it adds to any dish, it is a common base vegetable in most Indian dishes. Biotin is known to be abundant in onions. Most flavonoids, which are antioxidants, are concentrated more in the outer layers, so when peeling off the layers, remove as little as possible. Folic acid, Vitamin C, and Amino acid are all present. Vitamin C is a powerful antioxidant that also aids in the formation of collagen, which is responsible for the health of the skin and hair. It's found near yellow-brown-skinned vegetables.