How Exposure to Cold Air Brings On a Cold.

Colds are caused by a virus infection; usually the rhinovirus or one of a host of others. Cold air does not give you the virus, it's already in your respiratory system but held under control by the immune system.
The immune system is severely inhibited by exposure to to cold air or other cooling; the virus is much less affected so can gain strength and cause a symptomatic infection.
If we go out in cold weather without a hat and coat or sleep under an air conditioner we inhibit the immune system and the virus gets a foothold. We wake up with a sore throat, a runny nose or a cough with or without a fever. Full cold symptoms follow and last about a week.
It is important that to avoid a cold we should always protect the upper respiratory system with a cap, a scarf and a warm jacket. Babies and young children are particularly vulnerable because their immune system is not fully developed. For all children (especially blondes) it is particularly important to cover their heads, neck and chest when taking them out, even if for just a few minutes. The cold air cold shocks their upper airways (nose, throat, sinuses and bronchial sysyem) and they become ill. Always: !! A Hat and Jacket in cold weather !! Grandmother was right when she said wear a hat and coat when you go out in cold weather.