This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Sulphurous acid solution may be taken internally in moderate doses and well diluted without definite effects on the healthy body, unless it be the quenching of thirst and some refrigerant action. Insufficiently diluted, the solution excites local irritation of the digestive tract, some persons being more sensitive to this than others. The sulphites and hyposulphites in large doses increase peristalsis, and cause purging, though not so readily as sulphates.
Given during the pyrexial state, e.g., of remittent fever, sulphurous acid is said to lower the body-temperature.
Disinfectants and antiseptics generally, aid the action of sulphurous acid, but it is so readily oxidized that it is better used alone. Steam favors the aseptic action of the gas, and nitre added to the burning sulphur makes it more effective (Dewar).
All oxidizing substances alter the chemical constitution of sulphurous acid, and impair the peculiar properties of sulphites, especially when in solution. The mineral acids, including sulphuric, decompose sulphites and hyposulphites.