Coughing is a symptom that everybody experiences at some time in their lives. Coughing bouts can have various characteristics. It can be mild, severe, dry, wet, acute, or chronic. It is difficult to judge the seriousness of a cough from its character. Even a persistent coughing may not be the sign of a serious underlying condition. A cough can occur on its own or be accompanied by expulsion of sputum or blood, breathing difficulties, fever or night sweats.
For example, a mild cough may sometimes be associated with a serious and potentially fatal disease, whereas a severe cough may be due to some mild, self-resolving infection. Medical attention must be sought whenever cough is persistent, regardless of the intensity of the cough, especially if it is accompanied by symptoms like bloody sputum and difficulty breathing.
The process of coughing, also referred to as the coughing reflex, is an attempt by the body to clear the air passages (the throat, larynx, trachea, bronchi and the bronchioles). In this respect, coughing is similar to sneezing, which is aimed at clearing the nasal passages. The airways that extend from the trachea to the bronchi are lined by special pulmonary irritant receptors.
Stimulation of these pulmonary irritant receptors by a variety of factors elicits the coughing reflex. The cough subsides when the air passages are cleared of the irritant. Not all of these stimulating factors can be cleared by coughing. In some cases, even when the initial irritant is cleared, the airway irritation and cough may persist.
Types and Causes
Depending on the underlying cause, coughing can manifest in various forms.
Coughing can either occur alone or be accompanied by expulsion of phlegm or mucus. Cough that is not accompanied by any mucus expulsion is known as dry cough or non-productive cough. Cough that is accompanied by expulsion of mucus or phlegm is known as wet cough or productive cough. The sounds produced during dry and wet coughing have different characteristics.
In dry cough, there is no phlegm in the air passages blocking the flow of air. In wet cough, the sounds are modified due to the presence of phlegm in the air passages. In addition to coughing sounds, the presence of phlegm in the air passages also affects breathing sounds. Coughing may not be able to clear the phlegm entirely.
Wet cough is mistakenly thought to be more serious than dry cough. However, both productive and nonproductive cough can be caused by serious diseases. Just because the coughing sound doesn’t seem to indicate any phlegm accumulation should not be taken as a sign that the underlying condition is not serious. For example, pleural mesothelioma (a type of lung cancer) can present with a dry and painful cough whereas the common cold is not a serious condition that is characterized by a productive (wet) cough.
Read more on coughing up phlegm.
Acute and chronic cough
Another characteristic of cough that may differ between individual cases is the duration of the cough. Coughing may be acute, and persist only for a few days before subsiding. On the other hand, coughing may be chronic in nature, and persist for longer duration. It is usually assumed that chronic coughing indicates a more serious underlying condition compared to bouts of acute cough.
However, the duration of cough is not always a reliable indicator of the seriousness of the underlying disease. For example, viral infections such as common cold and flu differ in severity, but both may be characterized by acute signs and symptoms that include coughing, runny nose, fever, and a general malaise. Acute coughing may also be caused by a potentially lethal blood clot in the lungs (technically known as pulmonary embolism). On the other hand, chronic cough may indicate an easily treatable case of bronchitis.
Cough with bloody sputum
Sometimes, coughing may be accompanied by expulsion of a bloody sputum. The quantity of blood in the sputum may vary. In some cases, only a few small streaks of blood may be seen. The origin of blood could be anywhere in the oral cavity and the air passages. The sight of blood in sputum usually causes fear, and for good reason. Cough accompanied by a bloody sputum is a feature of serious diseases such as tuberculosis, lung cancer, and pulmonary embolism.
In fact, pulmonary embolism can turn fatal very quickly (within minutes or hours). However, it is important to note that blood in the sputum is not always an indication of a lethal disease. Treatable diseases such as pneumonia and bronchitis may also cause cough accompanied by expulsion of a bloody sputum. Regardless of the suspected cause, it is advisable to immediately seek medical attention if one notices blood in the sputum.
Cough with difficulty breathing
Coughing in some cases may also be accompanied by difficulty in breathing (technically known as dyspnea). The extent of breathing difficulty may vary depending on the underlying disease. Both serious and mild conditions may present with cough and breathing difficulties.
For example, coughing and dyspnea can occur in serious diseases such as pulmonary embolism, lung cancer, and tuberculosis. Manageable diseases associated with coughing and dyspnea include asthma, pneumonia, common cold, and bronchitis. Smokers are also likely to have frequent coughs accompanied by breathing difficulties.
Cough with night sweats and fever
Fever and night sweats may accompany coughing in both serious and mild diseases. For example, seasonal influenza is a manageable condition that can cause cough, fever, and night sweats. On the other hand, fever and night sweats may also occur in serious conditions such as tuberculosis and lung cancer.
Furthermore, excessive sweating in pulmonary embolism may be mistaken for night sweats. In some of these serious cases, fever and night sweats may precede the onset of cough. Therefore, it is advisable to seek medical attention even if a person does not have cough but suffers from fever and night sweats for many weeks.
Cough with colored sputum
The mucus expelled during a cough is known as sputum. Under normal conditions, sputum is either clear or whitish in color. Sputum also has a consistency that is thicker than water. Clear or whitish sputum may be seen in asthma, flu, and common cold. A change in the color of the sputum to yellow, brown, pink, orange, red or green may indicate a serious underlying problem that requires treatment.
Read more on mucus color.
For example, bleeding in the respiratory tract can result in expulsion of pinkish or reddish sputum. Old, dried blood may also give the sputum a brown or black color. Respiratory infections also change the color of sputum. Acute respiratory infections usually present with white or gray sputum, whereas chronic respiratory infections are characterized by yellow or green sputum.