Bitter herbs are thought to stimulate digestive function by increasing saliva production and promoting both stomach acid and digestive enzyme production.⁴ As a result, they are particularly used when there is low stomach acid but not in heartburn (where too much stomach acid could initially exacerbate the situation). These herbs literally taste bitter. Some examples of bitter herbs include greater celandine, wormwood, gentian,dandelion, blessed thistle, yarrow, devil’s claw, bitter orange, bitter melon, juniper, andrographis, prickly ash, and centaury.⁵. Bitters are generally taken either by mixing 1–3 ml tincture into water and sipping slowly 10–30 minutes before eating, or by making tea, which is also sipped slowly before eating.

Horehound contains a number of constituents, including alkaloids, flavonoids, diterpenes (e.g., marrubiin), and trace amounts of volatile oils.⁶ The major active constituent marrubiin and possibly its precursor, premarrubiin, are herbal bitters that increase the flow of saliva and gastric juice, thereby stimulating the appetite.⁷ Similar to horehound, elecampane has been used by herbalists to treat people with indigestion.

Carminatives (also called aromatic digestive tonics or aromatic bitters) may be used to relieve symptoms of indigestion, particularly when there is excessive gas. It is believed that carminative agents work, at least in part, by relieving spasms in the intestinal tract.⁸

The mucilage of slippery elm gives it a soothing effect for coughs. Usnea also contains mucilage, which may be helpful in easing irritating coughs. There is a long tradition of using wild cherry syrups to treat coughs. Other traditional remedies to relieve coughs include bloodroot, catnip, comfrey (the above-ground parts, not the root), horehound, elecampane, mullein, lobelia, hyssop, licorice, mallow, (Malvia sylvestris),red clover, ivy leaf, pennyroyal (Hedeoma pulegioides, Mentha pulegium),onion, (Allium cepa), and plantain (Plantago lanceolata, P. major). None of these has been investigated in human trials, so their true efficacy for relieving coughs is unknown.

Elecampane is a demulcent (soothing herb) that has been used to treat coughs associated with bronchitis, asthma, and whooping cough. Although there have been no modern clinical studies with this herb, its use for these indications is based on its high content of soothing mucilage in the forms of inulin and alantalactone.⁹ However, the German Commission E monograph for elecampane does not approve the herb for bronchitis.¹⁰

Traditionally, herbs that have a soothing action on bronchioles are also used for asthma. These include marshmallow, mullein, hyssop, and licorice. Elecampane has been used traditionally to treat coughs associated with asthma.¹¹

Mullein is classified in the herbal literature as both an expectorant, to promote the discharge of mucus, and a demulcent, to soothe and protect mucous membranes. Historically, mullein has been used as a remedy for the respiratory tract, particularly in cases of irritating coughs with bronchial congestion.¹² Other herbs commonly used as expectorants in traditional medicine include elecampane, lobelia, yerba santa (Eriodictyon californicum),wild cherry bark, gumweed (Grindelia robusta),anise(Pimpinella anisum), and eucalyptus. Animal studies have suggested that some of these herbs increase discharge of mucus.¹³ However, none have been studied for efficacy in humans.