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An occasional cough is normal, but one that persists could signal an underlying problem. Find out how to treat a cough at home and when it is time to seek help.

Brought on by an annoying tickle in the throat or congestion in the chest, a cough is not a disease in itself, but a defensive response to an invader. A cough — an explosive expulsion of air from the lungs — is the body’s way of ridding itself of foreign substances and secretions in the lungs or respiratory tract so as to reduce irritation or prevent infection.

A cough is a reflex mechanism. When a foreign substance or mucus stimulates the sensory nerves of the respiratory system, an impulse is sent to the "cough centre" in the brain. This triggers a message to the muscles in the respiratory system telling them to contract and force the irritant out of the body with a burst of air.

Types of Coughs

There are several types of coughs caused by different sources and infections.

• A stress cough is a reflexive spasm of the airways due to stress. There is no mucus and it is not associated with infections.

• A dry cough with no phlegm, and a scratchy or painful throat, can be due to a viral infection, cold, dry air or dust or smoke. The brain interprets throat irritation as a foreign object and triggers a cough to expel the perceived "invader".

• A productive, chesty or wet cough is one that expels phlegm. Phlegm or mucus is a thick protective fluid produced by the tissues in the mouth, nose, throat, sinus and lungs to trap germs and keep tissues moist. The colour and consistency of phlegm indicates the severity of an infection. Typically, thick discoloured mucus is an indication of infection. Chronic chesty cough with dark-coloured or bloodstained phlegm may be a sign of bronchitis, bacterial pneumonia, tuberculosis, and in some cases, lung cancer.

• A barking cough usually occurs in children and may be associated with croup or other viral infections. A "whooping" cough can indicate a serious infection and needs prompt evaluation by a doctor. Postnasal drip is a cough triggered by excess mucus (from a cold or flu) running down the back of the throat.

According to Dr Adeline Tan, Senior Consultant, Respiratory Medicine, Ng Teng Fong General Hospital, most coughs are caused by viral respiratory tract infections and resolve in a few days or within three weeks. A cough that lasts for more than eight weeks is considered chronic. “In adults, the most common causes of chronic cough include bronchitis, asthma, postnasal drip, sinus problems and acid reflux,” she explained.

Cough Medicines

A cough is often a sign of an underlying condition so it is important to identify the source of the cough for more effective treatment.

Over-the-counter medicines may be used to alleviate the discomfort associated with coughs. “These may be helpful in treating and soothing the symptoms of common cough – but only in cases when you are well and if the cough is not associated with breathing problems, wheezing, weight loss, chest pain or bloodstained phlegm,” said Dr Tan.

Cough medicines take several forms, she explained. “Cough suppressants control or suppress the cough reflex and work best for a dry, hacking cough that keeps you awake. Expectorants help in thinning the mucus and clearing thick mucus from the airways and may be used for a productive cough.”

For coughs that occur with cold symptoms, such as body aches and nasal congestion, you may opt for over-the-counter cough medicines that combine suppressants, expectorants, antihistamines or decongestants. “This combination of medicines may give optimal relief for multiple symptoms. The downside is that you may be taking medication which you don’t need,” added Dr Tan.

This means you should check the ingredients of cough medicines and speak to the pharmacist to be sure. This is especially important if you have any chronic diseases such as high blood pressure, diabetes and heart problems, and are taking any prescription medicines.

Do not take over-the-counter cough medicines for more than seven days.

How to Reduce Your Risk of Getting a Cough

You can reduce your risk of cough with basic hygiene, frequent handwashing, and by not touching your mouth or eyes. An annual influenza vaccine is also useful to prevent seasonal flu. The elderly and those with chronic lung disease should also consider being vaccinated against pneumococcal disease.

Lower the risk of chronic cough by not smoking and avoiding second-hand smoke. A healthy diet, regular exercise and sufficient water and sleep also go a long way towards a robust immune system to keep coughs and illness at bay.