Marshmallow Soothes Cough

An extract of marshmallow root (Althaea officinalis L., var. robusta), and the mucilaginous polysaccharide isolated from the root, demonstrated significant anti-tussive activity in an animal test (G. Nosal'ova et al., Pharmazie, 47: 224-26, 1992). Doses were administered orally and cough from both laryngopharyngeal and tracheobronchial stimulation was depressed. The mucilage was as potent as some non-narcotic anti-tussive drugs. Marshmallow syrup was also tested and was about 20 times weaker than the pure mucilage, as might be expected from the proportion of mucilage found in the syrup.

Comment

Mucilage is not changed by the digestive tract until it reaches the colon, where it may be partially or completely destroyed by bacterial action. Hence the anti-tussive effect of the mucilage found in marshmallow root must result from its presence on the gastrointestinal mucosa.

Herbalists believe that this demulcent action is a reflex effect carried from the digestive tract to the respiratory tract by the vagus nerve. In other words a soothing action on the upper gastrointestinal mucosa causes reflex soothing of the respiratory tract, leading to bronchodilation and reduced coughing. Although there is no direct experimental verification of this reflex, the above study provides indirect evidence. Other indirect verification comes from the fact that the reverse phenomenon as been noted -- gastrointestinal irritation causes bronchoconstriction and cough. For example, acid infused into the oesophagus causes vagal-mediated bronchoconstriction (L. Mansfield et al., Ann. Allergy, 47: 431-34, 1981) and a significant association between nocturnal asthma attacks and oesophageal reflux has been demonstrated in children (M.E. Martin et al., Ann. Allergy, 49: 318-22, 1982).

The British Journal of Phytotherapy.

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By Kerry Bone

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