How can allergys form in the human body?

Question: How can allergys form in the human body?
- Keywords:
  allergy,
  function,
  human body
Asked by anon-354687 on 8 Mar 2023. This question was also asked by anon-354663.
- Kirstie Andrews answered on 8 Mar 2023:
  
  This can happen when the immune system thinks something is a threat and harmful to the body (often by mistake). To fight off the threat and protect the body, the immune system produces antibodies against that substance, for example pollen, that release chemicals when the substance is detected again. These chemicals cause the symptoms of the allergy (called an allergic response).
- Edward Guy answered on 8 Mar 2023:
  
  Its a case of mistaken identity! An allergy happens when your immune system tries to fight something that should be harmless, but your immune system mistakes it for something dangerous. This ‘case of mistaken identity’ that triggers your immune response, makes you allergic to something harless, like pollen (hay fever)
- Katie Dexter answered on 8 Mar 2023:
  
  This is when your immune system (the part of you that fights off bacteria and viruses) thinks that something is a threat when it isn’t! Lots of people are allergic to pollen, and this means that when pollen in breathed in, your body overreacts and attacks the pollen. In reality, the pollen doesn’t do any harm.

Question: How can allergys form in the human body?