A food allergy is caused by the immune system reacting to a particular substance as if it
is under threat, and setting up antibodies to counter this threat.
Every time the sufferer comes into contact with this substance the immune system reacts,
usually within minutes.
Symptoms vary between sufferers, but often include itchy skin, swelling of the
bronchial tubes causing wheezing and other respiratory problems, gastric problems
such as vomiting and diarrhoea, and a sudden drop in blood pressure due to swelling
of the blood vessels.
In some people symptoms can be life threatening and may need to be treated
immediately with an intra-muscular injection of adrenaline.
A food intolerance is an adverse reaction to a food that does not involve the immune
system. Reaction can happen immediately or can be delayed up to 20 hours after the
food is eaten.
Symptoms of food intolerance can be vague, and can include gastrointestinal
problems such as bloating and wind, diarrhoea, and nausea. Food intolerance can be
similar to many other medical conditions, so it is important to be checked by a doctor
to eliminate any other possible problems.