Marshmallow root (Althaea officinalis) has been used in ancient Greek, Middle Eastern and ayurvedic traditions as an anti-inflammatory agent and to support lung function. Most of the side effects of marshmallow root are actually the same effect it's most valued for, soothing sore skin and membranes with a mucus-like substance and encouraging immune system function.
Marshmallow root is often found in cold and flu preparations, and is also used for bladder ailments and as a calming agent for the skin. The herb is full of mucilage, a slippery plant starch that coats dry throats and skin.
Respiratory Side Effects
Marshmallow root creates a slick, mucus-like surface on dry throats and mucus membranes. It will suppress coughing. Marshmallow could make congestion worse, as it acts like mucus in the throat and lungs. It should be used for hacking coughs, not wet, productive ones. Don't use marshmallow root with a medicine containing an expectorant, because the two medicines will work against each other.
Skin Side Effects
Marshmallow root can be used as a cream or poultice to treat psoriasis, eczema, diaper rash and dry skin. The herb produces a coating that soothes irritation and is useful for treating inflammation. In ancient Persia, it was used to treat sore gums in teething babies.
Inflamed skin is very sensitive, and cream application could cause redness, stinging or other side effects. Stop using a cream if it's uncomfortable, painful or you develop hives, which could mean you've developed an allergic reaction. If a poultice is made with boiling water, burns could result if the poultice isn't allowed to cool.
Bladder and Digestive Side Effects
Marshmallow root is a diuretic, which means it will cause your body to lose water. This side effect is actually part of the treatment, stimulating kidney function and flushing the bladder. Drink lots of water if using marshmallow root, and make sure you have access to a bathroom.
The root will lower stomach acid, which may make digestion more difficult. If you have hypochlorhydria or have had a gastric bypass operation, check with your doctor before using marshmallow root.
Marshmallow root can be taken as a tea, used as a cream or powder and has even been injected into the bloodstream by Japanese researchers. You can find marshmallow root on the shelf of a well-stocked grocery store in the herbal tea aisle in Traditional Medicinal's Throat Coat product.
The naturopathic Robert's Formula also contains marshmallow root, and can be found in health food stores for the treatment of bowel problems. Marshmallow root coats the intestines and encourages the immune system to eat and digest microbes. Read ingredients carefully, as many combinations of marshmallow root contain lots of sugar to make the herb more palatable.
It's been given to children and babies for centuries, and is generally very safe. The French even made it into medicinal candy, which is the origin of modern marshmallows.
Studies show that marshmallow root can lower blood sugar when injected into mice, and the European Union cautions diabetics to carefully monitor their blood sugar when using marshmallow root. Hot teas also can burn sensitive mucus membranes, so cool to a comfortable temperature before drinking.