Onions are a rich source of Sulphur. Sulphur is a key ingredient in keratin and it boosts the maintenance of collagen. Collagen is the skin structure that binds the hair follicle. Keratin and collagen are present in most parts of our body as they constitute the proteins which is the tissue that makes up our hair, nails, skin, internal organs and the like in our body. Keratin is a protein that builds the health of your hair. 95% of your hair is Keratin.