Onions being rich in sulphur help in the production of the collagen tissues, which in time will regenerate your hair follicles. Other than this, onions also stimulate circulation of blood, and help in keeping your scalp clean.
How to apply: Cut a few onions into small pieces and squeeze the juice out of them. Apply this juice on your scalp; keep it for at least 30-45 minutes, before applying a shampoo. Since onions have a pungent smell, you can add some rose water or some honey to it.