Living in a sociable houseshare has a downside: if one of us gets a cold, we all get a cold. However, there was one time when my housemates and my boyfriend all got the same cold which I somehow managed to avoid.

I obviously boasted about my amazing immune system and claimed that was the reason I did not catch anything. But I wanted to know what is really going on when we manage to avoid a cold everyone else gets.

On average, a person catches 200 colds in their lifetime. The reason we don’t catch every cold we come in contact with is our immune system, the billions of cells running through our bloodstream fighting off infection for us.

Immune system genes are inherited. In fact, the genes that vary the most from person to person are the genes that influence the immune system. Sometimes, our immune system will be good at fighting off a particular virus because of what has been inherited. Not getting a particular cold that everyone else gets does not necessarily mean that your immune system is better, it is just different.

There are things that can strengthen or weaken the immune system. Stress is a big thing that can suppress your immunity. It is fine in short bursts, like when you feel stressed before a job interview or something more exciting like performing on stage, or, I don’t know, fighting a lion. The flight or fight response is very important in some of those situations and stress is a part if that.

But prolonged stress is bad because it makes the body release cortisol and corticosteroids. These both suppress cells called lymphocytes, which kill invading bacteria and recognise harmful substances.

So, have good genes and don’t be stressed. Not things that are always within our control.

Luckily, exercise can give your immune system a boost but nobody really seems to know the exact reason why. Some theories are:

  • Exercise helps to flush the bacteria out of your airways, I guess from all that heavy breathing.
  • As your heart pumps faster, your antibodies get circulated more rapidly, which could help them catch diseases quicker.
  • Exercise helps to slow down the release of stress hormones, which, as previously mentioned, suppress your immune system.
  • Exercise increases the production of macrophages, which are cells that attack bacteria.

The other thing that is good for the immune system that I can really get on board with is sleeping.

If you don’t get enough sleep, you are more likely to get ill or take longer to recover from an illness. This is because when you sleep you release proteins which are needed if you have an infection. The antibodies in your immune system are also depleted when you are not sleeping.

So, maybe I did not catch that cold because I got lucky with my genes, or I had plenty of sleep or did a good amount of exercise. It did not stop me getting struck down with a cold last week, but you can’t win them all.