Marshmallow has been traditionally used for cough, inflammation of the mouth and stomach, and peptic ulcers. 

It appears to have antimicrobial and anti-inflammatory properties and may be used topically to increase epithelialization of wounds. It is also commonly used  to treat stomach ulcers, diarrhea, constipation, swelling of the stomach lining, and pain and swelling of the mucous membranes that line the respiratory tract