Meteovista.co.uk now calculates the risk of colds and flu as a result of the weather. In winter our resistance is often low. Why is this?
Dry air weakens our immune system
Cold air can hold less moisture. As a result of this the absolute humidity is lower than in the summer. In general, therefore, the air in the winter is relatively dry. In dry conditions, we are more susceptible to colds and flu. This is due to:
- The drying of mucous membranes which means that we produce less saliva. A moist nose and throat normally trap more airborne viruses. When our throat and nose are dry our immune system is therefore more susceptible.
- Viruses survive better in cold conditions. In dry conditions, there is less water vapour to become attached to virus particles, this means they remain lighter and spread through the air more easily.
Cold and lack of sunlight
Strong winds, rain, cold, large fluctuations in temperature and lack of sunlight are all factors which lower immune resistance. Lack of sunlight causes a reduction in vitamin D levels. Exposure to strong winds, rain and low temperatures causes the body to cool down, which puts extra pressure on the immune system.
Cold air constricts the blood vessels in the upper airways. This makes it harder for immune cells in the blood vessels to reach the places where viruses are most active. In this way cold conditions also weaken our immune system.