What Causes a Dry Cough That Will Not Go Away?

A dry cough that outlasts a cold is nearly always post-viral airway irritation: the virus has gone, but the lining of the airways is still inflamed and its cough receptors are set on a hair trigger. That version reliably settles, usually within three to eight weeks, and antibiotics do nothing for it because there is no bacterial infection to treat.

If the cough is still there beyond eight weeks, the explanation is usually one of three things, and none of them is the infection you started with.

Why the cough keeps going#

Cough is a reflex, and reflexes can become sensitised. After inflammation, the nerve endings in the airway respond to things they would normally ignore: cold air, laughing, perfume, dust, talking for a long time. Each cough irritates the airway further, which lowers the threshold again. That self-sustaining loop is the reason a cough can persist long after the cause has resolved.

The three common causes of a longer cough#

Reflux. Stomach contents reaching the upper esophagus and throat irritate the same nerves. Often there is no heartburn at all. Clues are a cough worse when lying flat, after large or late meals, or in the early morning, sometimes with a hoarse voice or constant throat clearing.

Asthma and airway inflammation. Cough-variant asthma produces cough without obvious wheeze. Clues are night-time and early-morning cough, cough on exercise or in cold air, and a history of eczema or hay fever.

Post-nasal drip. Mucus from the nose and sinuses running down the back of the throat. Clues are constant throat clearing, a blocked nose, and a cough worse on waking.

Two medicine-related causes are worth knowing. ACE inhibitors, a very common class of blood pressure tablet, cause a dry cough in a meaningful minority of users, sometimes starting months after beginning them. If that fits your timeline, raise it with your prescriber rather than stopping the tablet yourself.

Where you work matters#

Dust, welding fume, flour, wood dust, isocyanates in spray paint and cleaning chemicals all cause occupational cough and asthma. The single most useful clue is whether the cough improves on days off and on holiday and returns within a day or two of going back. If it does, tell your occupational health service. This is a recognized and preventable problem.

When it needs investigating#

Any cough lasting more than three weeks in a current or former smoker deserves a chest X-ray. So does cough with weight loss, drenching night sweats, persistent fever, or coughing blood. In regions where tuberculosis is common, a cough of more than two to three weeks with fever, night sweats or weight loss should prompt testing without delay.

What helps in the meantime#

Stop smoking and avoid vaping, which sustains airway irritation. Honey in warm water is a reasonable simple measure for adults. Treat a blocked nose properly. If reflux fits, eat earlier in the evening and raise the head of the bed. Give any single change two to three weeks before judging it.

The wider picture#

If reflux looks like the culprit, the fuller guide to acid reflux and bloating explains how it produces symptoms far from the stomach and what really settles it.