Putting food allergies into perspective - although up to 20% of the population claim to have a food allergy, this is actually only true for 1%.
The other 19% are most likely suffering from a non-allergic intolerance to a particular food or additive. In some cases, a person may develop a psychological aversion to a food, which has no physiological basis and which does not occur if the food is given without their knowledge.
True food allergy
True food allergies occur when an otherwise harmless protein within a food acts as an allergen, causing an overreaction of the immune system in sensitised individuals.
Over 170 different foods have been identified as causing allergic reactions, but some are far more common than others. When dealing with labelling and minimising the presence of potential allergens in food products, manufacturers tend to concentrate their efforts on what have become known as the 'big eight' and 'second eight'. These are the major serious allergens (MSAs).
Big eight
Milk, eggs, soy, wheat, peanuts, shellfish, fruits, tree nuts.
Second eight
Sesame seeds, sunflower seeds, cottonseed, poppy seed, molluscs, lentils, beans (except green beans), peas.
Additives such as tartrazine, sulphites and latex are also often classed as MSAs.
Food labelling
Although restaurants and food manufacturers are currently not required by law to label food products according to the content of potential allergens, the Institute of Food Science & Technology (IFST) recommend that warning be given voluntarily.
Most food products now display warning if they are found to contain an MSA, other than it simply being listed as one of the ingredients. In cases where it cannot be categorically stated that a food is allergen free, less specific warnings such as 'MAY contain traces of peanut' or 'Produced in a factory where peanut is also handled' might be given.
Even so, the recent revelation that as many as one third of people aged between 49 and 65 find it difficult to decipher food labels indicates that a tighter more universal method of labelling is needed.
Symptoms
Symptoms are usually systemic, leading to a generalised rash, itching, swelling, and sometimes difficulty breathing. In severe allergies, anaphylactic shock can result which can be life threatening due to restricted breathing and circulatory shock (see 'Anaphylaxis' section).
In oral allergy syndrome, which usually occurs alongside seasonal rhinitis (hay fever), eating particular fruits can lead to localised redness and itching in the mouth and throat.
Non-allergic adverse food reactions
Coeliac disease
Coeliac Disease, though commonly referred to as a food allergy, is not a true allergy but a Type IV, or delayed-type, hypersensitivity to gluten, found in wheat. People with Coeliac Disease suffer bloating and diarrhoea when they ingest any food containing wheat, and can become anaemic due to resulting malnutrition.
Food intolerance
Some people may react badly to particular foods without strictly being allergic to them. This is usually a result of intolerance to the food, either because the person is lacking a digestive enzyme, or because one of the additives in the food (e.g. tartrazine or monosodium glutamate) causes a non-immune adverse reaction. Where an enzyme is lacking, toxic by-products and histamine can build up and lead to what is known as a pseudo-allergic reaction, with accompanying inflammation. In some cases, intolerance may also mimic allergy through the abnormally fast absorption of natural histamine from the diet.
Reactions to toxins
In a small number of foods, such as mushrooms and fish, naturally occurring poisons may be present, which will cause a consumer to have an adverse reaction, simply due to the ingestion of a toxin.
In general, non-allergic adverse reactions are slower and less severe than true allergies, and they usually vary according to the amount ingested. Symptoms include rashes, bloating, vomiting and diarrhoea, abdominal pain, and sometimes palpitations.
Treatment
If you have a food allergy, especially if you are prone to anaphylactic shock, you need to avoid that food by shopping carefully, reading food labels, and where necessary quizzing restaurant staff!
If the food is eaten unknowingly, antihistamines will help reduce mild inflammatory symptoms such as rashes and itchy skin.
A person who appears to be suffering from anaphylactic shock should be treated immediately with an injection of adrenaline into the thigh muscle. If they are aware of their allergy, they will usually carry a preloaded syringe and be able to administer it themselves, but it is always best to get them to hospital as soon as possible. Once there, supplementary treatment of antihistamines or corticosteroids will be given to contain the reaction (see the Anaphylaxis section).
19/05/2009