Red Onion OIl Red Onion oil also helps in minimizing breakage & thinning of hair. Anti - Hair fall Onion oil helps effectively optimize the hair density cycle due to the presence of plenty of antioxidants which particularly work for boosting the functioning of certain enzymes that work together and help control hair fall. Onion oil is also rich in sulfur which reduces breakage, split ends and thinning of hair. Other nutrients present in onion oil reduce the oxidation of hair.