Dry Cough Causes: Post-Viral, Asthma and Meds

A dry cough brings nothing up. That single fact steers the investigation away from secretion and toward irritation: something is provoking cough receptors in an airway that has nothing to clear. Four explanations cover most cases — a recent infection, hyperreactive airways, acid, and a medication people rarely suspect.

The one that comes after being sick

The most common reason for a dry cough that refuses to end is the illness you already had. StatPearls describes subacute cough as driven by persistent irritation of cough receptors while airway or paranasal sinus inflammation is still resolving, and reports postinfectious cough in up to 25% of patients after a respiratory infection. MedlinePlus makes the same point about influenza specifically: the cough and the tired feeling may last for weeks.

The tell is direction. A post-viral cough should be fading week over week, even if slowly. One that holds exactly steady for two months is telling you something else is maintaining it.

Cough-variant asthma

Asthma is one of the three leading causes of chronic cough in adults, and it does not always announce itself with a wheeze. Some people have a cough and nothing else — worse at night, worse after cold air, worse after exercise, worse during allergy season. Because there is no wheeze to hear and no phlegm to show, this is one of the most commonly missed causes, and it is the reason lung function testing enters the workup for a cough with no obvious source.

The medication cause

ACE inhibitors, a widely prescribed class of blood pressure drug, produce a dry cough through a mechanism StatPearls attributes to bradykinin accumulating in the airway. Two details make it hard to spot:

• It can begin hours or weeks after the first dose, so the connection to a new prescription is easy to miss.
• It is purely dry and persistent, with none of the other features that would point to a disease.

If a nagging dry cough started somewhere in the vicinity of a new blood pressure prescription, that timing belongs in the conversation with your prescriber. Do not stop the medication yourself.

Reflux, drainage and dry air

Trigger	How it usually shows up
Gastroesophageal reflux	Worse lying flat or after meals; often without heartburn
Upper airway drainage	Constant throat-clearing, a tickle at the back of the throat
Dry indoor air	Worse overnight in heated or air-conditioned rooms
Smoke, dust and fumes	Tracks with a place or an activity rather than with time of day

Reflux and upper airway cough syndrome complete the leading trio alongside asthma, and both are frequently silent in every way except the cough.

In children

The duration rules are stricter for children: StatPearls sets the chronic threshold at more than four weeks for children aged 14 and younger, against eight weeks in adults. A dry night-time cough in a child that persists past that line, or that repeatedly follows exercise, deserves an asthma evaluation rather than another bottle of syrup.

When a dry cough needs investigating

• Coughing up blood — even a dry cough that suddenly produces blood
• Shortness of breath
• Unexplained weight loss, fever or night sweats
• A new or changing cough, or new hoarseness, in someone over 45 who smokes
• A cough that disrupts sleep or daily activity
• Anything past eight weeks in an adult, or four in a child

The full framework for how duration narrows the list is in persistent cough causes, and the opposite presentation — the one that brings something up — is covered in wet cough causes.

Easing it while the cause is identified

1. Fluids, which soothe an irritated throat even with nothing to clear.
2. A humidifier at night, the single change that helps most dry coughs.
3. Remove the irritants — smoke, strong fragrance, dust in the bedroom.
4. Raise the head of the bed if lying flat makes it worse.
5. Note the pattern — time of day, meals, exercise, cold air — and bring it to the visit.

This content is informational and does not replace medical consultation, diagnosis, or treatment. See also cold symptoms and flu symptoms.