An allergy is a reaction the body has to a particular food or substance. Allergies are very common. They're thought to affect more than 1 in 4 people in the UK at some point in their lives.
They're particularly common in children. Some allergies go away as a child gets older, although many are lifelong.
Adults can develop allergies to things they were not previously allergic to.
Having an allergy can be a nuisance and affect your everyday activities, but most allergic reactions are mild and can be largely kept under control.
Severe reactions can occasionally occur, but these are uncommon.