With the colder weather upon us we're likely to find ourselves dealing with more cold and flu viruses that lead to symptoms like a runny or blocked nose, sore throat, temperature, low mood, lethargy and headaches. Being exposed to the viruses behind colds and flu are almost inevitable, but for most of us our immune system is capable of fighting them off before we know we've been exposed to them. That's because our body has a very clever system built into it that recognises an