Although Tuberculosis (TB) and other lung infections are common throughout the developing world, they are not among the most common causes of chronic cough. Any acute or chronic infection that involves the sinuses, upper airways, lower airways, and lungs may lead to acute or chronic cough. It may also be due to allergies or air pollution. However, cough is one of the most common symptom of active TB affecting the lungs, but may be absent in cases of extrapulmonary TB (TB affecting organs other than lungs). Classically, the cough in TB lasts for more than three weeks, and may start as a dry irritating cough, which may be no different from that suffered in any chest infection. The cough of tuberculosis will continue for weeks or months getting progressively worse. After a while profuse amounts of sputum or phlegm may be brought up from the chest with each cough. If a blood vessel is damaged blood may be coughed up and this is known as haemoptysis. The cough of severe tuberculosis may be uncontrollable causing the patient to have spasms of wracking continuous coughing. Sometimes the patient will complain of pains in the chest which will be made worse by coughing. In severe cases, where much of the lung has been destroyed, breathlessness may occur.