Why do doctors advise salt water gargles during throat infections?
Sore throats are sore due to inflammation, caused usually by bacterial infection. These bacteria are also full of fluid. When you gargle with salt water, osmosis occurs. The higher concentration of salt in gargle helps to draw liquid or moisture out of your own swollen tissues of throat, relieving inflammation. Since the swelling is reduced it makes you feel better. The salt may also kill off some of the bacteria by drawing out moisture from the bacteria. However many strains are resistant to the mild levels of salt. So the salt water will not directly kill off all the bacteria. Gargling with salt water simply creates a dehydrated environment that the bacteria find less hospitable and potentially dangerous.
Salt is more soluble in warmer water. Hence for sore throats, frequent gargling with warm salt water is recommended to help reduce swelling and soreness.