If you’re a parent of young children, you’ll no doubt be on a merry-go-round of sickness. Runny noses, coughs, and fevers are standard, especially once nursery and school kicks in. But here’s the reassuring truth: this is perfectly normal. Each sniffle and sneeze is actually part of their immune system learning, adapting, and getting stronger. But how does a child's immune system work (and how can we help make it stronger?) 

A Child's Immune System: A Castle Under Construction

When babies are born, their immune system is like a newly built castle with only a handful of basic defences, mostly borrowed from their mother in the form of maternal antibodies. These inherited protections are part of the innate immune system: the castle’s immediate, general-purpose guards who protect against a broad range of invaders.

As children grow, their castle is gradually reinforced. The adaptive immune system acts as the specialised armoury and training academy within the walls. Each time a child encounters a cold or infection, the adaptive system develops new weapons - antibodies and memory cells - specifically designed to fight that particular intruder. Here are the main agents:

Fast-Response Defences: The Front Line 

While the armoury is still under construction, children rely heavily on innate defenders: the castle’s rapid-response guards. These early responders aren’t specialists yet, but they spring into action immediately to hold the line and prevent germs from advancing.

Mucosal Defences: The Castle Gates

The nose and throat act as the front gates. Layers of mucus, immune cells, and antimicrobial substances trap and neutralise invaders before they penetrate deeper into the fortress. Lactoferrin (the key ingredient of Leapfrog IMMUNE) is a protein that is a vital part of those fluids, killing bacteria and preventing viruses from attaching to healthy cells.

Phagocytes: The Patrol Knights

Macrophages and neutrophils roam the castle grounds, engulfing and destroying intruders, clearing debris, and sending signals to summon reinforcements. Lactoferrin is also stored in neutrophils, and when those neutrophils reach an infection site they release lactoferrin to help to quash the infection. 

Complement System: The Siege Weapons

Circulating proteins act like catapults and battering rams, punching holes in enemies, marking them for elimination, and rallying more defenders to the breach.

Natural Killer (NK) Cells: The Elite Strike Force

These specialised warriors hunt down infected cells, preventing invaders from using them to multiply.

B and T Cells: The Trainee Squires 

Finally, the adaptive apprentices step in. Inexperienced but highly adaptable, they study the intruder and craft specific weapons that are stored in the armoury for future battles. 

Adult vs Child Immune System - What's The Difference?

An adult immune system is like a fully fortified castle with a well-trained army and a stocked armoury. Over decades, it's faced countless invaders. The guards know exactly how to repel familiar attackers, often stopping them before they reach the inner walls. Memory cells act like battle maps and manuals, allowing the fortress to deploy defences instantly.

Children’s castles, in contrast, are still under construction. Walls are strong but incomplete, and the armoury is still being stocked. Each infection is like a new siege, teaching the defenders how to respond more effectively next time. Innate guards hold off the invaders, but without a seasoned strategy, intruders can still breach the gates and cause mild damage.

The Numbers Game: 200+ Cold Invaders

There are more than 200 different cold viruses out there, each with its own disguise and tactics. Unlike adults, whose bodies have already mapped many of these enemies, children are still learning to recognise each new face.

Every cold virus is like a mini siege. The innate guards rush in to contain the attack, while the adaptive apprentices scramble to study the invader and craft new weapons. Each siege survived strengthens the armoury and sharpens battle strategies, making future invasions easier to repel.

This ongoing “numbers game” explains why children seem to catch cold after cold. Their bodies are training, learning, and slowly expanding defences, turning each encounter into valuable experience for their immune army.

Why Leapfrog IMMUNE Is A Powerful Ally 

Toddlers and children can catch up to 12 colds per year. While each attack is a valuable training exercise for a child's immune system, it can be exhausting for parents, with sick days and time off school or social activities.