Fresh air is also an important factor. Spending time outdoors in fresh air helps destroy bacteria and promotes cellular resistance to infection. In addition, fresh air is an important help in reducing stress. And stress is a common cause of a weakened immune system. And, of course, fresh air improves the quality of the blood, thanks to its oxygen content. Blood
quality, as we have seen, plays a crucial role in the functioning of the immune system. That is why, when we exercise, we should make sure that we do not just breathe in the unclean city air, but instead try to get out into nature to breathe in the good air deeply. This has a very cleansing effect on the blood. Of course, living in the countryside would be optimal.

As already mentioned, the negatively charged oxygen ions, which are mainly found in the forest and near the water, are the best for optimal respiration. Exercise itself also promotes breathing. Another way to breathe in fresh air is to ventilate your rooms more often – especially by sleeping with the windows open. Because of the importance of oxygen, you should also be careful about covering your nose with masks. Your oxygen intake will be limited and you will be breathing in your own carbon dioxide (CO2) instead. This can have very negative effects on all sorts of health aspects. For example, lack of oxygen damages the brain, which in turn has other knock-on effects, including on the psyche. The psyche is also an important factor in strengthening the immune system, as we will discuss in the next section.