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Allergy or Intolerance?

When we have an adverse reaction to a certain food it is often difficult to know if the symptoms that we are experiencing are the result of a food ‘allergy’ or food ‘intolerance’.

Food Allergy

Food allergy is an adverse reaction by the immune system to a specific food and it is the involvement of the immune system which makes the food allergy serious even potentially life threatening. The body makes specific antibodies (IgE) to ‘fight off’ the allergens found in these foods, when the food is next eaten, or sometimes is in contact with the skin, it triggers an immune system response which results in the release of histamine and other naturally occurring chemicals in the body.

Symptoms caused by food allergy can range from rashes, generalised swelling (oedema) diarrhoea, vomiting, stomach ache, asthma, blocked or runny nose and hives (urticaria). In the most severe cases symptoms such as swelling of the lips, tongue or face, shortness of breath, throat constriction, breathing difficulties and loss of consciousness can occur.  This is known as anaphylaxis and is potentially life threatening.  Normally symptoms arise within a few minutes of eating or coming in to contact with the offending food, although they may be delayed by up to a couple of hours.

Thankfully true food allergy is actually quite rare with approximately 2.5% of the population diagnosed as suffering.  However should you suspect that may be suffering an allergic reaction to a food you should seek the advice of a professionally qualified allergy nurse or doctor who will be able to carry out the appropriate tests such as elimination and challenge, skin prick testing or specific IgE blood test, to determine if your symptoms are caused by an allergy. 

The foods that most commonly cause allergic reactions are Peanuts, tree nuts such as almonds and Brazils, eggs, milk, fish, shellfish, and sesame.

Food Intolerance

Food intolerance on the other hand is not so clear cut and is a much more controversial area, with many believing that intolerance is not important or for that matter even exists.  Although not life threatening it can and does make the sufferer feel extremely unwell and can have a major impact on working and social life.   Interestingly, those dealing with gastrointestinal disorders are aware of the increasing importance of food intolerance and a number of clinical studies are being organised.

Basically this is a much slower type of reaction to foods we eat (the reaction may be hours or even days later), and there is a tendency towards being associated with chronic inflammatory illnesses such as IBS, migraines, arthritis and skin problems.

Symptoms can last for many hours, often in to the next day and because it is quite common to be intolerant to several different foods at the same time it becomes very difficult to determine whether food intolerance is the cause of chronic illness, and which foods may be responsible. Many people with food intolerance have several symptoms. Often the symptoms are vague and not always easily diagnosed. People often complain of being in a fog, being lethargic, feeling bloated as well as being tired all the time. These are often additional to main problems relating to bowels, skin, joints, and headaches. On fact a person suffering with food intolerance may have one or many of the above symptoms.

Food intolerance can be caused by several different factors, modern lifestyles often lead us to eat the same type of food groups repeatedly, such as pasta, bread and cereals, and we eat in a hurry without giving our stomachs time to digest foods properly.  Some people actually lack the proper enzymes needed to break foods down as with lactose intolerance where the enzyme lactase is not produced to break down the lactose (milk sugars) in milk. Others react to the chemicals that are sometimes produced naturally in foods such as caffeine, salicylates, and histamine in foods like strawberries, chocolate and cheese.  Another possible cause of food intolerance is to additives in foods, these can be found in the form of sulphites which are added to processed foods to give them a longer shelf life.  They can also be found in fruit drinks and wine.

Again elimination and challenge is the gold standard but with an obvious difficulty if the reactions are not immediate as with classical food allergy. There is no such service provided by the NHS as yet, and mostly services provided are by the private sector.

There is no hard data on how many people are affected by food intolerance but it is likely to be several millions in the UK alone. Some estimates suggest it is as high as 45% of the population.

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