Allergy or Intolerance?
Adverse reactions to foods are often called many different names including food hypersensitivity, food intolerance, food allergy, and many other medical and non-medical terms. These names add to the confusion of diagnosing and managing food related problems.
By keeping a diary of all suspected food related reactions (written records, photographs and keeping labels of suspected pre-packed foods), this will help to identify which type of food is causing your symptoms. Sometimes the food triggers will be obvious whilst other reactions are very difficult to identify.
True food allergy is a reaction involving the immune system where the body sees the food as harmful and makes specific antibodies (called IgE antibodies) to ‘fight off’ the allergens found in these foods. This results in the release of histamine and other naturally occurring chemicals in the body. It is this release of histamine and chemicals, which produce the symptoms we recognise as an allergic reaction.
Symptoms caused by an allergic reaction to food can range from skin reactions: which include itching and rashes (urticaria); swelling (angioedema), gut symptoms, vomiting, stomach ache, diarrhoea. Respiratory symptoms such as coughing, sneezing, asthma, blocked or runny nose.
In the most severe cases symptoms may develop rapidly and can be life threatening so require urgent medical attention. Symptoms may include swelling of the lips, tongue, or face, shortness of breath, throat constriction and breathing difficulties. Loss of consciousness can occur in extreme cases. This collection of symptoms is known as anaphylaxis. Normally symptoms arise within a few minutes of eating or coming in to contact with an offending food, although they may be delayed by up to a couple of hours. Those at risk of anaphylaxis should have an adrenaline device available. The GP can prescribe this if it is necessary.
Thankfully true food allergy is actually quite rare, affecting approximately 2% of the adult UK population and up to 8% of children. Should you suspect that you or your child may be suffering from a food allergy, you should speak to your GP who will be able to help you or may refer you for specialist advice to a hospital allergy clinic.
The foods that most commonly cause allergic reactions are peanuts, tree nuts (such as almonds and Brazils), eggs, milk, fish, shellfish, and sesame. You should be aware that any food can cause an allergic reaction and some foods are more likely to cause reactions in certain ethnic groups.
Key points on food allergy
- Food allergy involves the body’s immune system and is a reaction to a specific food or foods
- Symptoms can be mild or severe and can involve the skin, gut, breathing or the whole body circulation
- Some GPs have the skills to diagnose and manage foods allergies. For the more difficult cases or where multiple or severe food allergy exist, referral to an NHS allergy specialist service in a hospital is recommended by NICE 2011 (the National Institute of Clinical Excellence)
- Patients with food allergy should be referred to a dietitian to help with the practical management of their food allergy.
- IgE food allergies are easy to diagnose and if the culprit foods are totally excluded it is possible to remain completely free from any symptoms.
- Reactions are often to trace amounts so complete exclusion is essential
- Some people can tolerate a well-cooked version of the food but will react to the food in its part-cooked or raw state. e.g. egg in a cake is often tolerated but the same person will react to boiled and scrambled eggs and mayonnaise.
Food intolerance is not so clear cut and is a more controversial area. Although not life threatening, it can and often does, make the sufferer feel extremely unwell and can have a major impact on working and social life. Ongoing symptoms can also affect the person psychologically as they feel they will never get better.
Food intolerance reactions do not involve IgE and the mechanisms are unclear however it is known that reactions are more likely to be delayed with the reaction occurring several hours and sometimes up to several days after eating the offending food. The symptoms caused by these reactions are numerous but have been associated with gut symptoms such as bloating, diarrhoea, constipation, and IBS, and skin problems such as eczema.
Symptoms can affect different people in different ways but usually last for many hours or days depending on the symptoms, and because it is possible 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. Sometimes the symptoms are vague and not always easily diagnosed. People may complain of non-specific problems such as brain fog, lethargy, headaches, or feeling bloated. These are often additional to bigger problems relating to bowels and skin.
Food intolerance can be caused by several different factors; lifestyles with erratic food intakes and poor nutritional intake or high intakes of refined foods, poor intakes of dietary fibre or high fat diets are just a few examples.
Some people actually lack the enzymes needed to break foods down for example lactose intolerance where the enzyme lactase is not produced in large enough amounts to break down the lactose (milk sugars) in milk.
Others react to the chemicals that are 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. A reaction to a food that has ‘gone off’ such as salmonella poisoning is another type of reaction to a food; such a reaction will usually affect anyone consuming it.
Key points on food intolerance
- Usually reactions are delayed and symptoms may take several hours, even several days to appear
- Multiple symptoms can occur be many and vary from migraine to bloating, diarrhoea, lethargy and a general feeling of poor health
- Chemicals in foods such as caffeine, salicylates, Monosodium Glutamate, and naturally occurring chemicals like histamines can also cause food intolerance reactions
- Reactions can occur after ingesting small amounts of a culprit food but are usually triggered by larger amounts – some people report they can tolerate a food if eaten once a week or in small daily portions but any more than this causes symptoms.
Getting a diagnosis
- Before commencing on an elimination diet you should consult your GP who may refer you to a dietitian
- To help with the diagnosis be sure to keep a food and symptoms diary.
Last update: October 2012