Why does alum work on blisters in the mouth/cold sores? Alum used to be an age old tradition to treat sores in the mouth and it worked beautifully.Foes anyone know why Alum works on sores in the mouth ?

Alum has been shown to be effective in treating aphthous stomatitis (canker sores) and it is believed to be due to the compound's **significant drying effect**. Alum is known as an astringent - a chemical compound that tends to shrink or constrict body tissues. More information on alum's astringent properties are reported in this paper. As the infected tissue shrinks there is a decrease in pressure due to swelling and this less pressure around the nerves in the affected area. The exact mechanism is still under question.