Yes Onion Juice can help for hair growth due to the Onion Juice promoting collagen production and also increases the blood supply to the hair follicles which helps your hair to grow.
Not only can onion juice promote hair growth studies have also shown that applying onion juice to your hair can help stop and reverse hair loss.
To use onion juice to help hair growth use your fingers and gently massage the onion juice into your scalp using circular movements and then Leave the onion juice in your hair for approximately 1 hour.
After an hour has passed you can then rinse the onion juice out of your hair with a mild shampoo preferably a nice shampoo with a nice fragrance to get rid of the pungent smell of onions.
You can make your own homemade onion juice at home.
To make homemade onion juice take some onions and peel the onions and cut them in 4 parts and then blend these pieces in a juicer/grinder
Next add a little water and then filter the juice using a muslin cloth.
Doing this will ensure that no onion chunks are stuck in your hair while you use the juice.