7. Avocados: Due to their high concentration of essential fatty acids naturally found in skin cells (which help to keep your skin smooth and supple), avocados are an age-old beauty secret. When topically applied to the hair and scalp, they have the added ability to stimulate collagen and elastin production. Mix a little avocado with sour cream (which contains lactic acid to help exfoliate dead skin and clean up buildup on the scalp) and apply to your hair and scalp for about ten minutes before washing it off.