While there are many healthy benefits to having a diet rich in this nutrient, L-cysteine hydrochloride as a supplement is sometimes used to prevent or treat symptoms of angina and possibly even HIV/AIDS. Though not conclusive, L-cysteine hydrochloride may help relieve some symptoms of chronic bronchitis. In clinical studies where patients with moderate to severe chronic obstructive pulmonary disease were given L-cysteine hydrochloride, flare-ups were reduced by 40%, while maintaining their regular therapies.