Marshmallow leaf and root are used for pain and swelling (inflammation) of the mucous membranes that line the respiratory tract. They are also used for dry cough, inflammation of the lining of the stomach, diarrhea, stomach ulcers, constipation, urinary tract inflammation, and stones in the urinary tract.
 
Cautions & Side Effects of Marshmallow Root:
Pregnancy and breast-feeding: Not enough is known about the use of marshmallow during pregnancy and breast-feeding. Stay on the safe side and avoid use.

Diabetes: There is a concern that marshmallow might interfere with blood sugar control. If you have diabetes, check your blood sugar carefully to avoid dangerously low blood sugar.