Introduction

Sometimes when people eat food their body reacts in an adverse way. This may be because they are allergic or intolerant to a particular food.

According to the NHS, around one or two people out of every 100 in the UK have a food allergy. However, food intolerances are more common.

Food allergies and food intolerances are defined differently.

Food allergy – this is when the body's immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious.

Food intolerance – this is much more common than food allergy and is not caused by the immune system.

The onset of symptoms is usually slower, and may be delayed by many hours after eating the offending food. The symptoms may also last for several hours, into the next day, and sometimes longer.

Intolerance to several foods or a group of foods is not uncommon. It can also be much more difficult to decide whether food intolerance is the cause of chronic illness, and which foods or substances may be responsible.