Science
What is an allergy?
An allergy is when your immune system overreacts to a normally harmless substance, like pollen or peanuts, treating it as a threat. The defensive response — sneezing, itching, swelling — is the body fighting something that isn't actually dangerous.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains an allergy.
Key things to understand
- 1The immune system mistakes a harmless substance for a threat.
- 2It releases chemicals like histamine, causing symptoms.
- 3Triggers ('allergens') include pollen, foods, dust, and pet dander.
- 4Reactions range from sneezing to life-threatening anaphylaxis.
- 5It's an immune misfire, not a sign of a weak immune system.
Frequently asked questions
- What causes an allergic reaction?
- The immune system wrongly flags a harmless substance as dangerous and releases chemicals like histamine, producing the symptoms.
- Why do some people have allergies and others don't?
- Genetics, early-life exposures, and environment all influence whether the immune system overreacts to particular substances.
- What is anaphylaxis?
- A severe, rapid, whole-body allergic reaction that can be life-threatening and needs emergency adrenaline (an EpiPen).