Most physicians are familiar with post-nasal drip from environmental allergies (allergic rhinitis) or irritant sensitivity (non-allergic rhinitis) and post-nasal drip from sinus infections as common causes of chronic cough. The airway is a remarkably interconnected system. The nose, sinuses, throat, lungs, esophagus, stomach, and the nerves controlling the cough reflex can all participate in keeping a cough going.
How Nasal Problems Can Keep a Cough Going
A cough may begin after a respiratory viral infection or an allergen exposure. Many assume that because the cough began after a single identifiable trigger, there is one "main" cause perpetuating it. The most common initiating factors for acute-onset nasal symptoms are viruses and allergens. When these triggers cause nasal congestion, the sinus drainage pathways can become obstructed, and mucus trapped in the sinuses can become overgrown by bacteria.
Nasal inflammation caused by bacteria then causes persistent nasal congestion, a runny nose, and post-nasal drip that often leads to a cough. If the initiating factor was a viral infection, it will typically resolve in under a week. Daily persistent congestion lasting more than a week suggests the presence of sinusitis.
Similarly, environmental outdoor allergen levels wax and wane and rarely cause daily persistent congestion — variable, intermittent congestion is more commonly noted. In contrast, indoor allergens such as pet dander, molds, and dust mites are present at more constant levels.
What Symptoms Suggest a Sinus Infection Is Present?
Several features can help identify when a sinus infection may be contributing to chronic nasal symptoms or a cough:
- Persistent colored mucus — pigment-secreting bacteria often give mucus its color; brown color is typically decomposing blood
- Not all bacteria produce pigments, so don't trust clear or white mucus to indicate the absence of infection
- Post-nasal drip that causes a sore throat is typically infected
- Prior allergy testing results can help rule out nasal allergy as a trigger — nasal congestion that occurs in summer is not being caused by Cedar pollen that blooms in winter
The Role of Sinus Rinsing When a Sinus Infection Is Suspected
Patients with sinus infections often improve when they use hypertonic saline for nasal washing (lavage). Doubling the salt content of mixable saline rinse bottles — such as a NeilMed squeeze bottle — can help, especially when used twice per day. Neti Pots are gravity-flow devices and tend to penetrate the sinus cavities poorly; they are not recommended at our office.
Sinus rinsing does not work if nasal congestion is so severe that no airflow occurs through a nostril. Afrin or other OTC decongestant nasal sprays (4-Way, Neo-Synephrine, etc.) can typically open a nostril within 30 minutes of use. The Afrin bottle specifically states it should not be used for more than 3 days — I usually warn patients not to use it for more than 2 days, and then only as needed. Never use Afrin in an open nostril.
Very important: overuse of Afrin will cause rebound congestion — one of the most persistent causes of recurrent nasal obstruction. Breaking the 2-day rule results in regret.
Distinguishing Allergic Rhinitis from Non-Allergic Rhinitis
Allergic rhinitis (also known as "hay fever") is caused by the production of allergic antibodies (IgE) that bind to mast cells found in mucous membranes — like the nose and eyelids. IgE is produced in some people in response to contact with environmental allergens; only about 30–40% of the population will ever make IgE. When allergens bind to IgE on mast cells, histamine and other inflammatory chemicals are released, causing typical allergy symptoms.
Non-allergic rhinitis (NAR) can cause very similar symptoms to allergic rhinitis (AR), however sneezing is less common with NAR. People with NAR commonly identify irritants such as fragrances, tobacco or wood smoke, cleaning solutions, Saharan dust, and diesel fumes as triggers for their nasal congestion and runny nose. It has been reported that 50–60% of people with AR also suffer from NAR.
Testing for Allergic Rhinitis
Allergic antibodies that cause AR can be identified by skin prick testing with allergen extracts or by blood testing (RAST or ImmunoCAP). Blood testing is expensive and is often limited by insurers to 30 tests per year. Skin prick testing for 80 allergens is often allowed each year.
Skin prick testing is done with a plastic device — not needles — does not cause bleeding, and rarely makes a 5-year-old girl cry. Results are available in 10–15 minutes after application. The accuracy of skin testing versus blood testing for IgE detection is essentially the same.
Treatment Options
Both AR and NAR typically respond well to a combination of a nasal steroid (Flonase, Nasonex, Nasacort, etc.) with a nasal antihistamine (azelastine, Astepro, Patanase). For severe AR, allergy shots are an effective option. There are also several effective avoidance measures for AR triggers that can reduce exposure to indoor allergens such as pet dander, indoor molds, and dust mites.
Post-Nasal Drainage Can Become Part of a Larger Cough Cycle
The problem becomes more complicated when nasal drainage is not the only contributor. A patient may have post-nasal drip from AR, NAR, or a chronic sinus infection that causes a cough, which then begins the cough–reflux–cough–reflux cycle. Sinus infections and viral infections are also common triggers for asthma, and mild asthma commonly causes a cough — cough-variant asthma.
At the same time, if a cough continues for a long period it can make the cough reflex increasingly sensitive. Once the sensory pathways involved in coughing become hypersensitive, stimuli that previously would have been insignificant may trigger a substantial coughing response.
A patient may begin coughing with:
- Talking or laughing
- Eating
- Smelling perfume
- Breathing cold air
- Lying down
- Swallowing
- A small amount of drainage
- A small amount of reflux
At this point, there is no such thing as the "main" cause for a cough.
The Problem With Treating Only One Cause at a Time
Treating a chronic cough sequentially with start-and-stop medication intervention trials is destined for failure. If a patient has post-nasal drip from a sinus infection, reflux, and cough-variant asthma, treating only one of those problems leaves the other triggers intact.
Three triggers require three treatments — but only one strategy works: they all need to be treated at the same time. A cough with three significant triggers cannot reasonably be expected to disappear when only one or two of the triggers are being treated.
The Bottom Line
Post-nasal drip from environmental allergies (AR), irritant sensitivity (NAR), or sinus infections can contribute to chronic coughing. If interventions for AR and NAR fail to work, an antibiotic may be an effective intervention for sinusitis.
If the presence of a sinus infection is in doubt, a sinus CAT scan is the definitive diagnostic procedure — never an X-ray.
This article is intended for general educational purposes and does not replace an individualized medical evaluation. If you have a persistent cough, consult your healthcare provider for a thorough assessment.