Q: What occurs when the immune system attacks a harmless substance that enters the body from the outside?


Read this paragraph and choose the correct option from the provided answers:

An allergy occurs when the immune system attacks a harmless substance that enters the body from the outside. A substance that causes an allergy is called an allergen. It is the immune system, not the allergen, that causes the symptoms of an allergy.

 Choices:

- panic attack

- nausea

- plague

- allergy


A:
allergy