Home / Hair Loss Treatments / Natural Treatments for Hair Loss / Cysteine Cysteine (Amino Acid) Hair Loss Treatment Type: Amino Acid Availability: Grocery and Health Stores. Notes: This amino acid is essential for proper hair growth. It likely does not help much to regrow hair if you have hair loss, but helps ensure that you have the proper nutrients necessary to grow hair. Claimed Results: None. Observed Results: Unknown. Clinical Results: Supports proper hair growth. Testing: Extensive for many things (other than hair loss). Safety Side Effects: None known. Gender: Either. Typical Costs: Varies.