Bromhexine works by encouraging the body's natural process for clearing mucus from the respiratory tract. It does this by increasing the production of serous mucus which is a thin type of mucus which dilutes the phlegm making it less hard and sticky. This also helps to 'lubricate' that hard phlegm which is already there – aiding the cilia (tiny hairs which line the respiratory tract) in sliding the phlegm out from the lungs. As well as being used on its own it is also included in a range of cough syrups.