ELI5: What causes allergies?

Imagine your body has a super cool security system called your immune system. It's supposed to protect you from bad guys like germs and viruses that can make you sick.

Sometimes, this security system makes a mistake! It thinks something harmless, like pollen from flowers or peanuts, is a bad guy. These harmless things are called allergens.

Here's what happens:

• Your body sees the allergen for the first time.
• It creates special helpers called antibodies specifically designed to fight that allergen. These are like little "wanted" posters for the allergen.
• You don't usually feel anything this time.

• The antibodies quickly grab onto the allergen.
• This triggers your body to release chemicals like histamine.
• Histamine causes all sorts of problems:

So, allergies happen when your immune system overreacts to something harmless, thinking it's a threat. It's like your security system being too good at its job! We don't always know why* some people develop allergies and others don't, but genetics (family history) plays a big role.