What are Food Allergies?An allergy is an inappropriate reaction by the body’s immune system to a substance that is usually safe. The human immune system is the frontline for fighting disease. When foreign material such as bacteria or a virus enters the body, the immune system reacts by producing an army of antibodies and specialised white blood cells. The army recognises the disease as being dangerous, and destroys it. It then retains a memory of that particular disease, so that it can recognise and destroy it, if it enters the body again in the future. An allergic reaction occurs when the immune system mistakenly recognises certain food as a dangerous foreign material, and incorrectly launches an attack. The initial exposure sensitises the immune system to that food, and any subsequent exposure produces the symptoms of an allergic reaction. The symptoms of food allergies range from mild to severe and can affect one or more parts of the body. They can occur at any time within 24 hours of exposure to the allergen, though more severe reactions occur within a short period of time. - Stomach and bowel - Vomiting, diarrhoea, abdominal cramping, failure to thrive (in infants), constipation and reflux.
- Skin - Eczema, urticaria (hives), swelling, lip and eye swelling, redness and/or atopic dermatitis.
- Lungs, chest and nose - Wheeze and rhinitis
- Anaphylaxis - The most rare kind of reaction, characterised by difficult/noisy breathing, swelling of the tongue, swelling/tightness of the throat, difficulty talking or hoarse voice, wheeze or cough, loss of consciousness, pale and floppy (in young children). Anaphylactic reactions usually occur immediately or within the first 20 minutes of exposure.
One way to identify food allergies is through elimination. The suspected allergen is removed from the diet for a number of weeks to ensure all reactions have ceased, and then reintroduced to identify any reaction. As food allergies are immune system responses, they can also be identified through skin prick and blood testing. In skin prick testing, small amounts of suspected allergens are applied to scratches on the skin (usually on the arm). If swelling and redness occur, an allergy is identified. Alternatively, a blood test (or RAST test) can identify the presence of antibodies in the blood which also suggest food allergies. Once diagnosed, food allergy is managed by the complete elimination of all sources of the offending food from the diet. This can be difficult, as food labelling is not always clear. The page entitled About our Food - Free From provides information about common allergens and how to avoid them. What is Food Intolerance?Unfortunately, the term ‘food intolerance’ is often confused and interchanged with the term ‘food allergy’, as the symptoms are often similar. However the difference between the two lies in the cause. Unlike food allergy, food intolerance does not involve an immune system response. Food intolerance can occur when: - a person’s body lacks the enzyme needed to break down certain food in the small intestine, or
- the body has an adverse reaction to certain chemicals, either naturally occurring or added, in the food.
Food intolerance is not life threatening, as some allergies can be, however the symptoms can be debilitating for the sufferer. The symptoms can be more vague than those resulting from food allergy, and may be confused with other medical problems. They may include: - Diarrhoea or constipation
- Abdominal pain or distension
- Indigestion
- Tiredness, sleep and concentration disturbances
- Headache, joint pain
- Depression or behavioural problems
- Eczema, asthma
Food intolerance is harder to diagnose than food allergy. No specific tests exist for the diagnosis, and practitioners usually rely on elimination diets to identify offending foods. Once identified, food intolerance can be managed through avoiding foods which cause symptoms. Some food intolerances are genetic and related to a person’s race. For example, lactose intolerance is most common in people of African and Asian descent. Genetic intolerances are usually permanent disorders. As these symptoms are vague and varied, it is important to rule out any other medical conditions before diagnosing food intolerance as the cause. What is Coeliac Disease?Coeliac disease is a rare but serious disease caused by sensitivity of the small intestine to a protein called gluten, which is present in wheat and other cereal grains, including rye, barley and oats. Left untreated, coeliac disease damages the lining of the small intestine, leading to impaired absorption of food, known as malabsorption. The small intestine is lined with tiny, finger-like projections, called villi, whose function is to break down and absorb nutrients in food. In untreated coeliac disease, the lining of the intestine becomes inflamed and flattened, reducing the surface area of the intestine, and limiting the absorption of the nutrients and minerals from food. This leads to deficiencies in vitamins, minerals and sometimes calcium, proteins, carbohydrates and fats. Like food allergy, coeliac disease is an immune system response, therefore it can be detected by a blood test for the presence of gluten antibodies and anaemia. A biopsy of the lining of the small intestine will confirm the diagnosis of coeliac disease. Coeliac disease can occur at any age, with symptoms developing gradually. These may include: - weight loss or failure to gain weight (especially in infants)
- very pale, floating faeces that have an unpleasant smell
- diarrhoea or constipation
- pale skin, breathlessness and lack of energy due to anaemia
Coeliac disease is managed through the complete avoidance of food containing gluten, such as bread, cereal, biscuits and pasta. The page named About Our Food – Free From lists foods and ingredients that contain wheat and gluten. References |
