Today, we’ll look at what onion seed oil can do for hair and Benefits of Onion Seed Oil for Hair. This oil comes from the flowers of onions and is often found in places like China and Southeast Asia. The dark-colored seeds come from the flowers and are widely sold. Companies that make medicine and beauty stuff use oil from these seeds in different hair things like shampoo and oils. This includes products for washing your hair or keeping it healthy. These things are usually made by well-known companies.