How your immune system reacts to colds and flu viruses

Phew – this is a big topic! We will try to simplify it as much as possible, because who has the time to get into the nitty gritty of a very complex system? Let’s get started.

Part one: the innate (natural) immune system
This is the defence mechanisms you are born with, so you don’t need to have encountered an invader (like a virus) for it to kick in. In the cells lining your respiratory tract you have receptors that act like guards – they recognise viruses that cause colds and flu and immediately trigger an immune response (more on that later).

Part two: the adaptive (acquired) immune system
This is the part of your immune system you may be more familiar with – when white blood cells encounter an invader (in this case viruses), destroy it and remember what it looks like in case it shows its face again.

Part three: triggering an immune response
Once the guards in the cells lining your respiratory tract recognise a virus, they send word to any white blood cells around, which then rally, multiply and march towards the infected cells. Once there, they get to work destroying the infected cells. As the cells are destroyed some white blood cells get a good look at the virus, and make antibodies so they will remember it for next time.

A key player in the immune response is inflammation. When an infection is detected your body sends more blood to the area, allowing more immune cells to travel there for the Battle Royale. This results in redness, warmth and swelling, which also has the added bonus of containing the infection to one area. Once the fight is over, other components of the immune system help ease the inflammation and heal any damaged tissues. So, while inflammation can be frustrating, it’s a sign your immune system is working.

Causes of a weakened immune system

Like Goldilocks found out with her bears, your immune system can be under-active, over-active or just right.

If it’s under-active it’s not functioning correctly and could leave you vulnerable to infections. Under-active immune systems can be inherited from your family (thanks guys!), be caused by medical treatments or be triggered by another disease. If you’re concerned that your immune system may be under-active, don’t try to self-manage but have it checked out by your doctor instead.

An over-active immune system is a bit too keen to do its job. This can happen when your immune system overreacts to things (known as allergens) like foods, insect bites, pollen or medications. It can also happen when your immune system gets confused and starts to think normal components of the body are invaders – this is known as an autoimmune disease, which should be managed by a healthcare professional.

Ways to support the immune system

Your immune system is a huge entity, so the best way to support it is to follow healthy-living strategies. These include things like:

  • Don’t smoke (if you do smoke – quit)
  • Eat a healthy, balanced diet
  • Exercise regularly and maintain a healthy weight
  • Get enough sleep
  • Do what you can to prevent getting an infection – like washing your hands regularly
  • Practice stress relief techniques to minimise stress

When you or your family do get sick with colds and flu, consider products that provide relief of the symptoms as well as support immune system function. The DEMAZIN range includes products containing zinc, a micronutrient known to play a role in almost every aspect of the immune response. So you can help keep your immune system healthy!

Frequently asked questions about the immune system and colds and flu


DEMAZIN Kids 2+ Cough + Immune Defence Syrup and the NEW DEMAZIN Kids 2+ Cold + Flu + Immune Defence Liquid contain zinc to help support healthy immune system function.


Despite what your own mother probably told you, you can’t get sick from being cold (within reason, it’s still not a good idea to go skiing in shorts). However, when the weather turns colder people tend to huddle together inside, making it easier for colds and flu viruses and other bugs to pass from person to person. This is why it is so important to maintain good hygiene.


In a way, yes. Once you’ve been exposed to colds and flu viruses, your immune system remembers them, so next time you encounter that particular virus your immune response is swift and decisive. This is why immunisation helps prevent you from getting sick. Your body develops antibodies to the parts of the virus in the vaccine, so if you encounter it for real your immune system jumps into action and destroys it before it can make you unwell.


Children’s immune systems are not exactly weaker than adult’s, they are more like a blank slate. Because they have not yet been exposed to many viruses, they don’t yet have the acquired immunity an adult has. This is one reason why kids seem to get sick so often.


Symptoms of a common cold (sore throat, headache, sneezing, nasal congestion and cough) tend to peak at about day 2 or 3 after the infection, and can last 7-10 days, but in some cases linger for more than 3 weeks.