A review of 39 clinical trials of NAC (N-acetyl cysteine) found that 400 to 600 mg per day was a safe and effective treatment for chronic bronchitis.¹ NAC supplementation was found to reduce the number of aggravations of the illness in almost 50% of people taking the supplement, compared with only 31% of those taking placebo. Smokers have also been found to benefit from taking NAC.² In addition to helping break up mucus, NAC may reduce the elevated bacterial counts that are often seen in the lungs of smokers with chronic bronchitis.³ In another double-blind study, people with chronic bronchitis who took NAC showed an improved ability to expectorate and a reduction in cough severity.⁴ These benefits may result from NAC’s capacity to reduce the viscosity (thickness) of sputum.⁵

The thymus gland plays a number of important roles in the functioning of the immune system. Thymus extract from calves, known as Thymomodulin®, has been found, in a double-blind study, to decrease the frequency of respiratory infections in children who were prone to such infections.⁶ The amount of Thymomodulin used in that study was 3 mg per kg of body weight per day.

In a double-blind study of elderly patients hospitalized with acute bronchitis, those who were given 200 mg per day of vitamin C improved to a significantly greater extent than those who were given a placebo.⁷ The common cold may lead to bronchitis in susceptible people, and numerous controlled studies, some double-blind, have shown that vitamin C supplements can decrease the severity and duration of the common cold in otherwise healthy people.⁸

Vitamin C and vitamin E may prevent oxidative damage to the lung lipids by environmental pollution and cigarette smoke exposure. It has been suggested that amounts in excess of the RDA (recommended dietary allowance) are necessary to protect against the air pollution levels currently present in North America,⁹ although it is not known how much vitamin E is needed to produce that protective effect.

Geranium (Pelargonium sidoides) is an herbal remedy used in Germany, Mexico, Russia, and other countries for the treatment of respiratory tract and ear, nose, and throat infections. In a double-blind study of adults with acute bronchitis, participants given an extract of geranium had a significantly shorter duration of illness, compared with those given a placebo.¹⁰ No serious side effects were seen. The amount of the geranium extract used in this study was 30 drops three times per day, taken before or after meals for seven days.

Anti-inflammatory herbs may help people with bronchitis. Often these herbs contain complex polysaccharides and have a soothing effect; they are also known as demulcents. Ivy leaf is approved in the German Commission E monograph for use against chronic inflammatory bronchial conditions.¹¹ One double-blind human trial found ivy leaf to be as effective as the drug ambroxol for chronic bronchitis.¹² Ivy leaf is a non-demulcent anti-inflammatory.

Anti-inflammatory herbs may help people with bronchitis. Often these herbs contain complex polysaccharides and have a soothing effect; they are also known as demulcents. Plantain is a demulcent that has been documented in two preliminary trials conducted in Bulgaria to help people with chronic bronchitis.^13,14 Other demulcents traditionally used for people with bronchitis include mullein, marshmallow, and slippery elm. Because demulcents can provoke production of more mucus in the lungs, they tend to be used more often in people with dry coughs.¹⁵

Expectorant herbs help loosen bronchial secretions and make elimination of mucus easier. Numerous herbs are traditionally considered expectorants, though most of these have not been proven to have this effect in clinical trials. Anise contains a volatile oil that is high in the chemical constituent anethole and acts as an expectorant.¹⁶

Anti-inflammatory herbs may help people with bronchitis. Often these herbs contain complex polysaccharides and have a soothing effect; they are also known as demulcents. Chinese scullcap might be useful for bronchitis as an anti-inflammatory. However, the research on this herb is generally of low quality.¹⁷

Antimicrobial and immune stimulating herbs may also potentially benefit people with bronchitis. Echinacea is widely used by herbalists for people with acute respiratory infections. This herb stimulates the immune system in several different ways, including enhancing macrophage function and increasing T-cell response.¹⁸ Therefore, echinacea may be useful for preventing a cold, flu, or viral bronchitis from progressing to a secondary bacterial infection.

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.¹⁹ However, the German Commission E monograph for elecampane does not approve the herb for bronchitis.²⁰

Caution: Do not use eucalyptus oil internally without supervision by a healthcare professional. As little as 3.5 ml of the oil taken internally has proven fatal.  

Eucalyptus leaf tea is used to treat bronchitis and inflammation of the throat,²¹ and is considered antimicrobial. In traditional herbal medicine, eucalyptus tea or volatile oil is often used internally as well as externally over the chest; both uses are approved for people with bronchitis by the German Commission E.²²

Expectorant herbs help loosen bronchial secretions and make elimination of mucus easier. Numerous herbs are traditionally considered expectorants, though most of these have not been proven to have this effect in clinical trials. Horehound has expectorant properties, possibly due to the presence of a diterpene lactone in the plant, which is known as marrubiin.²³

Lobelia contains many active alkaloids, of which lobeline is considered the most active. Very small amounts of this herb are considered helpful as an antispasmodic and antitussive agent (a substance that helps suppress or ease coughs). Anti-inflammatory properties of the herb have been demonstrated, which may be useful, since bronchitis is associated with inflammation in the bronchi.²⁵ Lobelia should be used cautiously, as it may cause nausea and vomiting.

Expectorant herbs help loosen bronchial secretions and make elimination of mucus easier. Numerous herbs are traditionally considered expectorants, though most of these have not been proven to have this effect in clinical trials. Mullein has been used traditionally as a remedy for the respiratory tract, including bronchitis. The saponins in mullein may be responsible for its expectorant actions.²⁶

Anti-inflammatory herbs may help people with bronchitis. Often these herbs contain complex polysaccharides and have a soothing effect; they are also known as demulcents. Plantain is a demulcent that has been documented in two preliminary trials conducted in Bulgaria to help people with chronic bronchitis.^27,28 Other demulcents traditionally used for people with bronchitis include mullein, marshmallow, and slippery elm. Because demulcents can provoke production of more mucus in the lungs, they tend to be used more often in people with dry coughs.²⁹

Expectorant herbs help loosen bronchial secretions and make elimination of mucus easier. Numerous herbs are traditionally considered expectorants, though most of these have not been proven to have this effect in clinical trials. Pleurisy root is an expectorant and is thought to be helpful against all types of respiratory infections. It is traditionally employed as an expectorant for bronchitis. However, owing to the cardiac glycosides it contains, pleurisy root may not be safe to use if one is taking heart medications.³⁰ This herb should not be used by pregnant women.

Thyme contains an essential oil (thymol) and certain flavonoids. This plant has antispasmodic, expectorant (mucus-expelling), and antibacterial actions, and it is considered helpful in cases of bronchitis.³¹ One preliminary trial found that a mixture containing volatile oils of thyme, mint, clove, cinnamon, and lavender diluted in alcohol, in the amount of 20 drops three times daily, reduced the number of recurrent infections in people with chronic bronchitis.³²

Vitamin C and vitamin E may prevent oxidative damage to the lung lipids by environmental pollution and cigarette smoke exposure. It has been suggested that amounts in excess of the RDA (recommended dietary allowance) are necessary to protect against the air pollution levels currently present in North America,³³ although it is not known how much vitamin E is needed to produce that protective effect.