Why do young children catch so many colds?
Because their immune systems are inexperienced, and because they are placed in exactly the circumstances that spread respiratory viruses most efficiently.
The numbers. Young children average six to twelve respiratory infections a year, and more in the first year of nursery or school. Adults typically have two to four. So a child with a runny nose most of the winter is usually within normal range, exhausting though that is.
Why so many:
There are hundreds of distinct viruses. Over 200 viruses cause the common cold, with rhinoviruses alone comprising more than 100 serotypes. Immunity is largely specific to each one. An adult has accumulated immunity to many through years of exposure; a three-year-old has met almost none of them. Every infection is genuinely new.
Immune memory is built by infection. There is no shortcut — the immune system learns by encountering pathogens.
Behaviour. Young children touch everything, put objects and hands in their mouths, do not cover coughs reliably, and have close physical contact with each other. Nursery and school concentrate this.
Anatomy. Children have narrower airways and shorter, more horizontal Eustachian tubes, which is why colds more often progress to ear infections in children than in adults.
Does starting nursery early help later? Studies suggest children in group care have more infections early and somewhat fewer in the first school years — the total is broadly redistributed rather than reduced.
What actually reduces transmission: handwashing, keeping children home when genuinely unwell, and not sharing cups and utensils. Vitamin C and echinacea have weak evidence at best.
When to seek advice: breathing difficulty, persistent high fever, dehydration, unusual drowsiness, a rash that does not fade under pressure, symptoms worsening after initial improvement, or infections that are unusually severe, prolonged or accompanied by poor growth.
Antibiotics do nothing for viral colds.