IT'S that time of year again... everyone is starting to cough and splutter as the cold weather rolls in.
It's an unavoidable fact of winter, but when does your constant hacking cough become something to worry about?
A cough is a reflex to clear mucus or other irritations from our throat.
In most cases it will be nothing to worry about, and will disappear in a couple of weeks.
But if your cough lasts more than two to three weeks, or is causing chest pain and shortness of breath, it could be a sign of something more serious and you should speak to your GP, experts warn.
A cough that has lasted several weeks and isn't showing signs of improving can be a sign of something more serious, like lung cancer.
Here's what your cough, and the colour of your mucous, could mean for your health...
1. Wet cough
A wet cough is caused by a build-up of mucus in the back of your throat, Dr Sarah Jarvis, GP and clinical director of Patient.info, told The Sun Online.
It can either be a persistent chesty, hacking, nagging cough or a cough that comes and goes.
And the build-up of phlegm in your throat can mean a number of things, depending on its colour.
Though grim, a green or yellow mucus is nothing to worry about, it simply means your body is fighting an infection.
"Unless you have chronic obstructive pulmonary disease (COPD) then having yellow or green phlegm does not mean you need antibiotics," Dr Jarvis said.
"What it means is your body's immune system is rushing to the spot and creating cells to fight off the infection.
"If you have COPD then there is a good chance it means you have a bacterial infections because people with COPD are much more likely to have bacteria living on their lungs, and that may mean you need antibiotics."
COPD is the name for a group of lung conditions that cause breathing difficulties, including emphysema and chronic bronchitis.
Symptoms of COPD include breathlessness, a persistent chesty cough and frequent chest infections.
Rust coloured mucus indicates blood and is far more serious, Dr Jarvis warned.
The most common causes for coughing up blood include a prolonged cough, a chest infection or something more serious.
"That could mean pneumonia or other things like tuberculosis," Dr Jarvis said.
"Or a clot on the lung, something called a pulmonary embolism, and of course lung cancer although that's not common.
"It certainly needs checking out."
If blood in your phlegm is also accompanied with chest pains and shortness of breath you need urgent medical attention.
Your body produces mucus regardless of whether you are sick or not.
It is a protective barrier along our nasal cavity that helps trap irritants like dust, smoke and bacteria.
In a healthy person their mucus should be a clear problem, so if you notice you are producing a bit more it's just your body's way of protecting you from germs.
You also produce more mucus when it is cold to help warm the cold air you breathe in so it is not so harsh on your lungs.
2. Tickly cough
Tickly coughs are those that don't produce any mucus.
They are often the result of irritation in the throat and mainly caused by viral infections like a cold or flu.
Some medication can also cause a tickly cough.
"Tickly coughs can be for several reasons, one of the reasons you need to think about is a medication called ACE inhibitor," Dr Jarvis said.
CLEAR IT UP Tips to banishing that tickly cough for good, including wearing a scarf, stopping talking and gargling vinegar
"It is a very common blood pressure tablet and it can cause dry, tickly, irritating coughs which often come on up to a year after you start taking the tablet.
"A viral infection will also be dry and irritating."
Pre-existing lung conditions like asthma can also contribute to coughing.
Dr Jarvis added: "Asthma can also have a dry cough but you will also have wheeze or shortness of breath with it.
"If it is asthma it will often get worse when you exercise or worse at night."
Sonia Munde, Asthma UK’s head of helpline and nurse manager, added: "If you have asthma and you have a flare-up of coughing, wheezing, breathlessness, tightness in the chest or wake at night with a cough it could mean that your asthma symptoms are getting worse and you need to take action, especially if you’re needing to use your reliever inhaler (usually blue) more than once every four hours.
"If you have these symptoms and you haven’t been diagnosed with asthma you should see your GP to find out if you have the condition."
3. Chesty, dry cough
A hacking cough is a short, dry but frequent cough.
It can be incredibly irritating to deal with.
Tens of thousands of Brits are currently battling a nasty, hacking cough that is sweeping the nation as the cold weather continues.
Make sure you keep an eye on it though as it could be a sign of something more serious, like pneumonia.
"A hacking cough which becomes fruity [has more mucus] is something you often see in things like COPD," Dr Jarvis said.
"That tends to be associated with shortness of breath when you exercise and sometimes with wheezing and chest tightness.
"Pneumonia often starts off as a dry cough but it will become more fruity and that is when you should start to think about if you are getting problems when you breathe, shortness of breath, problems when you breathe in deeply especially."
4. Spasm coughing
A spasm cough is when you experience intense bouts of coughing, almost like your throat is going into spasm.
It can come along with common illness like the flu, but there is a surprising reason you may experience this cough.
"Harsh spasms of coughing are often worse at night and that can be reflux," Dr Jarvis said.
"Stomach acid will reflux back into the back of your throat and it can cause up to between two and five cases of chronic cough.
"It tends to be worse if you lie down flat and it tends to be associated with heartburn and a nasty acid taste in the back of your throat."
5. Whooping cough
Whooping cough, or pertussis, is a respiratory infection caused by bacteria called Bordetella pertussus.
It can affect anyone at any age but can be life-threatening in babies and young children.
In recent years cases of the illness have spike in the UK and vaccines have now been made available to pregnant women.
The vaccine became available on the NHS to pregnant women in 2012 after a whooping cough epidemic hit the country, as well as other parts of the globe.
There were more than 9,300 cases of whopping cough reported in the UK alone that year - more than 10 times more than the number of cases recorded in previous years.
Mums who have the vaccine reduce their baby's chance of contracting the deadly condition by 90 per cent.
"A lot of adults don't actually get the whooping noise, but you get spasms of coughing that last for a few minutes that leave you gasping for breath," Dr Jarvis said.
"It is usually dry, it is really hacking and it is really severe.
"Unfortunately it is known as the cough that lasts 100 days for a reason.
"You tend to start off with the classing sneezing, runny nose, eyes watering like a normal virus but then after about a week or so you start to get the hacking and it gets worse.
"We can give antibiotics to reduce the chance of you passing it on to other people but sadly they do not necessarily get rid of the cough."
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