Allergies.

A reader recently asked why "...Western life makes children allergic to everything?". After reviewing my immunology notes from last week, I have this to say:

Children are too clean and are not getting sick enough. My professor's advice was to try to get children sick as much as possible (without being cruel!) when they are young.

When young children don't get exposed to enough pathogens, their bodies are not able to properly build up their immune system. Up until the age of seven, the immune system is learning and strengthening itself. ("What doesn't kill you, makes you stronger" is a very true expression!). If, while developing, the immune system is not exposed to enough "true invaders" (e.g. bad bacteria, viruses), then it starts to consider normal molecules (e.g. nuts, dairy, bananas) dangerous and elicits an immune response against these foreign (but safe) molecules.

Also, did you know that there are no allergies or asthma in most parts of Africa? This is likely due to the fact that African children are exposed to SO much when they are young (e.g. bugs are eaten in meals, baths are taken in dirty ponds, no one washes their hands after using the washroom). As a result, there immune systems get very good at detecting what is a real threat and what is harmless.