The Cough Reflex
Coughing is a complex protective reflex which is the normal means of cleansing the bronchi, the airway tubes to the lungs, of excessive fluids or unwanted matter. It is associated with other protective processes such as mucus secretion and narrowing of these tubes. Coughs are usually initiated by a irritation in the bronchi. However, coughs can also result from irritation in the ear canal or to the pleural membrane around the lungs. Causes of coughing include inhaled irritants, inflammation, infections, fibrosis, blood clots, tumors, or lung congestion from heart insufficiency. Infections are by far the most common cause of acute coughs.

In the absence of a coughing, material is normally expelled from the respiratory tract by the action of small hairs on the inner surface of the respiratory tubes which continually move the coating of mucus at rates of up to one centimeter per minute. This mucus coating is an important defense mechanism, since it collects and moves waste matter and inhaled particles away from the lungs. Respiratory fluids are normally produced by small glands and goblet cells in the bronchi. These fluids prevent irritation of the cells lining the respiratory airways.

A number of factors can interfere with the function of the airway lining and produce the need for coughing. Inflammation from irritants or infection can increase respiratory fluid production and the number of immune defense cells, and leading to excessive sputum production. The number of goblet cells in the bronchial membrane increases in chronic bronchitis or after chronic exposure to mild irritants. In people exposed to tobacco smoke or other inhaled irritants the movement of the small hairs is reduced, mucus production increases, lung cleansing is diminished, and the airways narrow. Viral infections can interfere with the motion of the small hairs and make the respiratory fluid thicker.

Reducing exposure to irritants, especially by stopping smoking, is an important means to avoid arousing the cough reflex. Adequate hydration is essential to avoid drying of the membranes. Simple steam inhalation can be adequate for reducing coughs due to irritation of the respiratory airway below the throat. For infections a number of different types of remedies can be of benefit.

Dry and Productive Coughs
Most acute infections of the respiratory tract are viral and recovery can be rapid and spontaneous. The coughs of viral infections are at first dry and spasmodic, but small amounts of white, thick sputum are usually produced as they progress. This type of cough can either be relieved with cough suppressants or made productive by using expectorants. Acute dry coughs may also be due to inhaled irritants or from a blood clot passing into the lungs. Chronic dry coughs are noninfective, usually due to either fibrosis or congestive heart failure which needs to be specifically treated.

As the sputum from respiratory infections becomes thick and more abundant, the cough becomes productive. Productive coughs usually occur after several days with a bacterial infection of the bronchi and last about a week. These coughs become persistent and reoccur periodically in cases of chronic bronchitis (inflammation of the airway tubes in the lungs). Chronic coughs with clear or dirty sputum are most likely due to a long-standing irritation such as from smoking. Sputum colored with pus is indicative of a secondary bacterial infection, although a yellowish sputum may be caused by an allergic response. Bacterial respiratory infections should be treated with antiseptic compounds or, in the case of pneumonia, antibiotics.

Cough Suppressants
Since productive coughs are a necessary means of removing the infectious and obstructive material, cough suppressants called antitussives should only be used for dry coughs. The exception would be when the cough is completely exhausting the patient or preventing sleep. Codeine is the most popular and frequently prescribed cough suppressant. Since it also dries the respiratory mucosa, narrows the respiratory tubes, and is a mild respiratory depressant, it can also aggravate some respiratory conditions. It may also cause nausea, vomiting, and constipation as well as produce sedation, physical dependance, or tolerance. The effective suppression of coughs by codeine should not prevent a more specific treatment of the cause which will give permanent results instead of only temporary relief.

Coughs originating above the voice box can be appropriately treated with soothing demulcents. Licorice (Glycyrrhiza) extract is usually thought of as simply a demulcent with a pleasant flavor, but its derivatives have been shown to have a central antitussive effect similar to codeine. Licorice is also considered to be a sedative expectorant. In addition its constituents have shown antiviral and immune-stimulating effects. About 30 drops of the fluid extract is used per dose. (Every 15 drops of any fluid extract is equivalent to 1 gram of the powdered herbal remedy.) However, long-term use of large amounts of licorice is hazardous since this can lead to potassium loss and high blood pressure.

An antitussive that works by reducing irritation of the respiratory membrane at or below the voice box is wild cherry bark (Prunus). Wild cherry bark is effective for nervous coughs and is often used in short-term infectious cases or when convalescing. The compound prunasin in wild cherry bark can be toxic in large amounts but in smaller quantities relieves the irritation of the mucosa and thereby alleviates coughing. From 20-40 drops of the fluid extract is normally taken. About 1 1/3 ounce of good quality bark must be used and extracted by 1 quart of room temperature water (not by boiling) to make the tea which is taken in 2 ounce doses. A wild cherry bark syrup preparation is used in 1-2 teaspoon doses but must be carefully preserved to be of maximum value.

Demulcents and Expectorants
Demulcents contain mucilaginous components that are used for their soothing effect on irritations of the membrane lining the throat. For this purpose cough syrups are commonly employed, in addition to acting as a vehicle for other antitussives or expectorants. Besides sugar in syrups and lozenges, other commonly used demulcents are honey, glycerin, licorice, and gum arabic (Acacia), since they also sweeten medicinal preparations. Coughs due to acute inflammation or from phases of increased irritability in chronic bronchitis can be treated with mucilaginous herbs in the dose necessary to gain relief. The soothing effects of these herbs are only present when prepared as extracts by soaking in water at room temperature. Coltsfoot leaf (Tussilago) is effective in these cases. Its low content of toxic alkaloids is safe when taken for short-term use. Marshmallow root (Althea) and slippery elm bark (Ulmus) are other sources of mucilage for allaying inflammation and alleviating coughs. Water extracts of mullein flowers (Verbascum), besides providing demulcent and expectorant effects, inhibit influenza viruses. Mullein leaf extract is also used for its demulcent mucilage in irritation from persistent coughs, whether dry or productive. The juice of plantain (Plantago) has a demulcent mucilage as well as antibacterial components. Another of its components enhances resistance to infection.

Expectorants, cough remedies that increase the amount of respiratory fluid secretions, can be used for both dry and productive coughs. Those known as sedative expectorants are used for dry coughs to increase respiratory fluid which produces a demulcent effect on the respiratory membranes. Stimulant expectorants help decrease the thickness of the secretions in productive coughs, thus aiding their expulsion, and inhibit bacterial growth by their antiseptic effects. Some sedative expectorants can also be use for productive coughs, but stimulant expectorants are considered too irritant for most dry coughs. Expectorants provide no direct benefit for coughs arising from irritation in the throat or to the pleural membrane outside of the lungs.

Sedative Expectorants
Sedative expectorants are used when the membrane is dry, sensitive, reddened, and swollen or when there is thick, scanty, adherent mucus in the airway tubes. These remedies have an antitussive action by increasing the amount of respiratory fluid, thereby producing a soothing effect on the bronchial membranes, and by decreasing the thickness of membrane secretions, thus facilitating their removal. The term sedative applies to their effect on the bronchial membrane irritation which causes coughing, not to their effect on the body or the mind. Some are called nauseant or irritant expectorants since they produce vomiting in large doses and they work by a reflex action due to irritation of the stomach lining. This gastric irritation causes an increase in membrane secretions in the bronchi. The nauseant expectorants ipecac (Cephalis), bloodroot (Sanguinaria), and lobelia (Lobelia) contain active alkaloids that can be toxic in large doses.

Ipecac is used both to liquify thick, tenacious mucus from the airways and to relieve spasms of the respiratory tubes, particularly spasms from croup. It reduces bronchial swelling and distress, and the coughing becomes easier. The main application for ipecac is in bronchial congestion with a dry, irritable cough. Ipecac is especially indicated when there is irritation with a continued effort to clear the larynx. It may be the best expectorant for acute conditions when taken in small, frequent doses insufficient to cause nausea. An appropriate dose for the syrup of ipecac used as an expectorant would be 4-8 drops given every two hours. This is much less than the single 1-2 tablespoon dose taken as an emetic.

Bloodroot is used for harsh, dry coughs with constriction or constant irritation or tickling in the throat. Its alkaloids produce a direct antitussive effect on the CNS cough center. Bloodroot is stimulant to the bronchial membranes, overcoming congestion and increasing membrane secretions. Considered too harsh a remedy for young children, it is used for acute or chronic bronchitis or laryngitis (inflammation of the voice box) when membranes are atonic after active inflammation has subsided. In these cases bloodroot is used even when there is abundant secretions. The expectorant dose of the tincture is 5-30 drops, while 1-3 teaspoons will cause vomiting. Bloodroot and lobelia have both been found useful for the persistent, harassing cough following influenza.

Lobelia is used in cases of respiratory spasm such as croup, as well as coughs due to irritation. It is specific for bronchial asthma. It promotes expectoration and improves respiration in acute bronchitis with coughing, especially where there is thick mucus with tightness and difficulty breathing. The potent antispasmodic action of lobelia helps avoid trapping of the sputum and assists in its expulsion. The expectorant dose of the tincture is from 5-20 drops, whereas the dose causing vomiting is from 1/2-2 teaspoons. Lobelia is often combined with cayenne when used as an antispasmodic.

Cayenne (Capsicum) acts as a gastric irritant because of its local action and stimulates contractions and secretions in the respiratory tract as well. The initial narrowing of the airways produced by its short-term use requires that it be used together with an antispasmodic. It inhibits the cough reflex and has been used internally as an antitussive. Small doses (5 drops of the tincture) are combined with other remedies and diluted with water.