Newswise — One of the classic cold symptoms is a cough. When coupled with a runny nose, sneezing, sore throat and fatigue, it can make you feel pretty miserable.

Usually after a week or so, the cold runs its course and most of the symptoms go away. But for some people, the cough hangs around a little longer.

So why do we cough and what can we do about it?

Jonathan Parsons, director of the Asthma Center and division director in the Division of Pulmonary, Critical Care and Sleep Medicine at The Ohio State University Wexner Medical Center, explains five things you should know about that persistent cough.

1. Coughing is a protective reflex.

Humans developed the ability to cough over time to do a number of things. One is to eliminate things that are in the lungs that cause irritation. We’ve learned to cough to expel the mucus that may be down there. Another is to protect your airway from anything going into your lungs so you don’t choke.

"We’ve all had the experience where we take a drink and it goes down the wrong pipe, we cough and it comes spraying out of our nose or mouth. That’s a reflex mechanism that we’ve developed to protect our airway," Parsons said.

2. The cough could be due to an upper respiratory tract infection.

Sometimes there’s still some residual airway inflammation in the lungs from typical upper respiratory tract infections. So even after the real meat of the infection is gone and you’re starting to feel better, you have this cough because you still have some inflammation in the lungs. The lungs are quite sensitive, so when they are inflamed and irritated, it doesn’t take a lot to cause a cough.

"If you have an infection, it’s always good to drink plenty of fluids. Staying hydrated with help thin out the mucus in your lungs and sinuses to help you get it out of there easier. If it’s thick and sticky, it’s hard for you to cough it out of your lungs or blow it out of your nose. If it’s thinner, it’s easier to expel," Parsons said.

3. Coughing can be worse at night.

If you’ve got an upper respiratory tract infection with any kind of sinus congestion or runny nose, when you lay down to go to bed, the mucus drains down the back of your throat on top of your upper airway, which causes you to cough.

Coughing at night is more disruptive because you’re trying to sleep. If you’re coughing throughout the day, you cough and you continue with your activities. When you’re trying to fall asleep, coughing can make it really hard to sleep, so it’s more irritating and frustrating for you and, potentially, your bed partner.

"For some patients, their cough is so severe that it disrupts their sleep to the point where they aren’t getting any sleep at all, which impacts their ability to function during the day. In that situation, you might consider taking a cough suppressant with codeine to blunt the cough reflex and assist with sleep," Parsons said.

4. If you’ve been coughing for more than three weeks, you may have a chronic cough.

"When you’re in the middle of an infection and you’re coughing, it doesn’t seem like it’s ever going to end. It’s frustrating but it’s a normal, protective and self-limited reflex," Parsons said.

If you’re still coughing and feeling sick after three weeks, then you should probably be evaluated. Make an appointment to see your primary care doctor. If necessary, your primary care doctor will refer you to a pulmonologist.

In our cough clinic, the definition of a chronic cough would be a cough that is persistent for more than three weeks. That usually will extend past most viral infections or any other respiratory infection. The common causes that we see are:

  • uncontrolled allergies, animal and environmental
  • uncontrolled asthma
  • side effects to medicine, including some blood pressure medications and non-steroidal medications like ibuprofen and aspirin
  • acid reflux where acid comes up from the stomach and irritates the upper airway while you’re sleeping, causing a persistent dry cough the next day

5. A persistent cough could be a symptom of a serious illness.

There are warning signs that you should seek medical care for a persistent cough before three weeks have past.

"If you’re coughing up blood, spiking fevers or have significant shortness of breath associated with the cough, you need to be evaluated quickly. You could have walking pneumonia. If you’re a smoker, it could be cancer. A doctor will examine you to determine the cause of the cough and establish a treatment plan," Parsons said.