When you get a runny nose and when this comes on suddenly it is most likely either a viral infection or an acute allergy flare up. Here are a few clues that might help you decide, and knowing what you have helps know what to expect and how to treat.

Viral Infection Clues

If you have been around young children or people who are sick (have the crud), then a viral infection is most likely. Viral infections can differ from illness to illness, so you can't always assume that you know what it feels like. There are hundreds of different viruses and they can have different presentations. Sometimes they may cause more congestion, sometimes more sore throat, sometimes more runny nose.

Viral infections often start in one place, (one side of nose, throat, chest) and then over the course of one or two days spread to the rest of the upper airway. People often produce large amounts of initially clear nasal mucous.

When in doubt, it is safest to assume that an acute onset of nasal obstruction is from a viral infection. You should assume that you are contagious and wash your hands frequently to reduce that chance of spreading the virus. Especially when there is some possibility that it is allergic, I would usually treat it as if it is viral but consider adding antihistamines into the treatment plan. Also, when copious clear drainage is the most bothersome symptoms, you can benefit from the drying side effects of the first generation antihistamines.

Acute Allergic and Non-Allergic Rhinitis Clues

If you have had some obvious exposure to allergens, then an acute allergy flare up is possible. An acute case of vasomotor rhinitis is also possible. The symptoms are generally short lived once the exposure is eliminated.

Common acute allergy exposures
Hay Fever" i.e. sudden pollen blooms
Mold Spore exposure - cleaning damp areas and gardening in damp compost and mulch
Large dust mite exposure
Exposure to animal dander
Common non-allergic rhinitis exposures
Perfumes, solvent fumes, smoke, dust

Allergic and non-allergic rhinitis often has a history of previous similar experiences that are also short lived. Sneezing, itchy red eyes, lack of sore throat, and lack of cough are clues that such an exposure may be to blame. If you do not get this type of airway obstruction frequently and if there is no obvious exposure to some irritant, then allergic and non-allergic rhinitis is not likely the cause

When runny nose is the main problem and when this is a chronic problem a couple of common issues come to mind.

Allergies can cause chronic rhinorrhea. The type of allergies that are year round are called Perennial Allergic Rhinitis, some seasonal allergies can last for months and if you are allergic to agents that are present in different seasons, the problem can be year round. Examples of allergens that cause persistent symptoms are dust mite, mold spore, pet dander, and cockroach antigen. This type of allergy may vary by location. People with indoor year round allergies may do better outside or in different buildings.

Non-allergic rhinitis can have drainage as its primary symptom. Non allergic rhinitis is a syndrome where you have the symptoms of allergy or chronic infection, but its is not actually an allergic reaction or infection. In some cases there are inflammatory cells present, despite no explanation for the inflammation. This problem treats best with nasal steroid sprays and occasionally anti fungal irrigations. A type of non allergic reaction to mold spore may be the primary cause of both this syndrome and or chronic sinusitis, this is a hot current topic in the field.

A sub category of non allergic rhinitis is called Vasomotor Rhinitis This problem is characterized by a sensitivity to one or more of the following: smells, air temperature changes, fumes, or smoke.

Treatment for chronic runny nose can start with OTC antihistamines and allergy sprays (not decongestant sprays). Other helpful safe medicines for this problem are the prescription sprays. The best prescription spray for runny nose is called Atrovent Nasal .03% spray. It is the only drying agent that comes as a spray. It is very safe and the most common side effect is that it can dry things too much, but that wears off quickly and can be avoided by trying a smaller spray next time or avoiding sniffing the spray back. Atrovent doesn't help congestion very much.

If congestion is also significant, then Astelin spray or the Nasal Steroid sprays may be more helpful.

Clear nasal drainage (especially one sided) that follows a significant head injury or nasal surgery needs to be discussed with your doctor. Rarely this can be a sign that the spinal fluid around your brain is leaking into your nose. The bone that separates the nose from the brain is surprisingly thin.

In some cases, after sinus surgery, especially some of the older techniques, patients will pool mucous on the bottom of the maxillary sinus and later it presents suddenly in a small sudden amount.  This is usually thick and viscous but can be thin and watery.

Post nasal drip (PND) that has just begun can be from several possible causes. An acute viral infection can start with a feeling of post nasal drip but it usually progresses to more prominent symptoms such as rhinorrhea or nasal congestion. Acute allergic exposures likewise could cause PND but usually there are other more prominent symptoms. Sometimes a mild bacterial infection will cause only a sensation of post-nasal drip, such problems usually resolve without medicine; other times they become persistent.

An acute flare up of acid reflux can cause a sensation of PND. This is surprising to many people because they usually expect that there would be heartburn and indigestion also, but that is not usually the case. The possibility that PND can be caused by acid reflux (technically called Laryngo-pharyngeal reflux LPR) is covered below more completely.

If PND is the only symptom and the duration so far is short, I would recommend treating with: saline rinses, non drying antihistamines (Claritin), Prilosec OTC 20 - 40 mg AM and PM, and if you have them, steroid nasal sprays. If things worsen or are still present at 8 - 10 days you should see a doctor to assist in the diagnosis.

If post nasal drip is a chronic problem and is the primary symptom, several things come to mind.

Nasal source

Sometimes, one or more of the posterior "deep" sinuses becomes chronically infected with bacteria. This can also happen in the adenoid pad region. The drainage from this problem is irritating and usually creates a characteristic redness in the back of the throat that can be seen on physical examination. If patients fit this pattern, they should see a specialist.

If chronic infection is suspect, the first step is usually to treat chronic sinusitis with prolonged broad spectrum antibiotics and steroid sprays or pills. If allergies are suspected, antihistamines or steroid nasal sprays are tried.

If a nasal source is highly suspect, and the diagnosis remains unclear, a CT scan of the sinuses is often obtained.

Non-nasal source

People think of chronic infection and allergy as the primary sources for PND. If PND is chronic and not associated with many other nasal symptoms, I think that it is much more common for it to be secondary to LPR = (Laryngo-pharyngeal reflux). This is a form of acid reflux that primarily affects the voice box area.

People rarely believe this at first, usually because they haven't considered it before and they may not have any heart-burn or indigestion.

The symptoms of LPR include one or more of the following and differ from patient to patient. Surprisingly, heart burn and indigestion are not usually present.


Common symptoms of LPR

A feeling of thick mucous in the throat
A feeling of a lump in your throat when you swallow, especially when swallowing "dry"
Hoarseness or a voice that fatigues easily
Chronic cough or throat clearing
Chronic sore throat, low in throat near voice box
Waking up choking or with burning
More likely if overweight or snore loudly or if you have sleep apnea


What to do if this describes your problem?

If the problem is severe or seems to be getting worse, you should see a specialist. An endoscopic exam of your larynx can help rule out the unlikely possibility of a throat cancer, and can provide information that can substantiate the LPR diagnosis, or perhaps suggest a different diagnosis. If the problem is likely to be LPR, the next "test" is to treat with high dose antacids, and see if there is any relief from the symptoms. If the doctor thinks that it is more likely a chronic infection, then a course of specially selected antibiotics will possibly be given or a culture of the nasopharynx can be done to identify the possible bacteria. If improvement isn't found, a CT scan may be helpful.


If you want to try and treat this yourself for a while, I would start by using saline nasal rinses and also high doses of antacids. Not just any antacid. It is well appreciated that treatment of LPR can be difficult and the results can be slow to come. You should get Prilosec OTC® and take 2 of them in the morning, and 2 of them in the evening. I would recommend taking them at this rate for at least 2 weeks and probably for 4 weeks before drawing any conclusions. This type of medicine is expensive, even the OTC form.

Proton pump inhibitors, PPIs, like Prilosec, have a good safety record in general but recent studies raise some questions about long term use. The usual full prescription dose is the same as 2 of the OTC form, taken only once a day. Using this medicine twice a day is "off label", but it is frequently needed to get control of symptoms in patients with LPR, especially at the beginning treatment.   Prilosec and others like it need to be taken about 30 minutes before a meal.  They are less effective if taken at other times.

The first month on antacids should be considered a test. Most often this therapy is begun on an "educated guess". One of the best ways to finish the diagnosis of LPR, is to get a good response from acid control medicines. It is best to begin treatment with the best medicines, given in higher doses. Usually, once the symptoms have resolved, a lower dosage is effective to keep symptoms from coming back.