Gargling with warm salt water helps a lot with cough and cold. In case of sore throat the tissue of the throat gets swallon or inflamed with the accumulation of the fluids in them causing a condition called edema. Salt water tends to pull the water away from the inflamed tissue. When the concentration of salt outside the tissue increases the water from the within the tissue moves out to balance the salt and the water concentration. Thus as water is expelled from the tissues, inflammation is reduced, thereby providing temporary relief.
Salt water also acts on the mucous lining of the throat. The mucous contains the irritants, allergens, bacteria and viruses which cause infection. Salt kills and removes all these infection causing agents and helps mobilizing the thick mucus lining which provides relief. Salt water creates an in hospitable environment for bacteria and thus keeps bacteria from growing again. Warm salt water gargles to relieve an aching throat but using excessive salt while gargling has it side effects. Saline water with high salt concentration draws more water from the lining of the throat. Thus gargling with excessive salty water should be avoided. Usually one tsp. (5g) of salt should be dissolved in 1 cup (250 ml) of warm water for instant relief.