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Food Hypersensitivity In Children

16 Apr 2007 7:44 AM - The Weekender

'Food Hypersensitivity' is defined as an adverse reaction to a food protein that results from a over-reaction of the Immune System. Food Hypersensitivity is different to 'food intolerance' which refers to an adverse reaction to food caused by chemicals contained in food, rather than an immune reaction. Examples of food intolerance would include lactose intolerance (reaction to milk sugar due to lack of an enzyme in the intestine).

Food hypersensitivity is common, affecting up to 6% of children and almost 2% of adults. The majority of food hypersensitivity reactions are caused by egg, milk and peanuts (actually a legume, not a nut), tree nuts, wheat, soy, fish and shellfish. In children, allergic reactions are most common to egg, cows milk, peanuts, tree nuts and soy. Food hypersensitivity reactions can either be rapid (lgE mediated) occuring within 30min to 1 hour after ingestion, or they can be delayed (usually non-lgE mediated) where symptons develope several hours to days after ingestion of the food. The rapidly occuring allergic reactions can be most dangerous and usually involved reactions on the skin (hives, itch, red patches) and intestines (vomiting, diarrhoea, abdominal pains). Severe lgE mediated allergic reactions can lead to potentially fatal effects in teh airways (wheezing, construction of upper airways, severe tounge/mouth swelling) and circulation (severely lower blood pressure and circulatory shock). This severe end of teh spectrum is known as 'anaphylaxis' and can be rapidly fatal if not treated aggressively and in a short time after occurances. In children, anaphylaxis occurs most commonly with exposed to egg and peanut products.

Young babies may show food hypersensitivity reactions to cow's milk protein, soy protein and goat's milk protein. Exposure in the first 6 months of life occurs through the mother's diet in breastfed babies or formula  in bottle fed babies. These babies may be more irritable than normal, cry a lot and be hard to settle. they may sem to be in pain a lot and may have vomiting and diarrhoea. In severe cases, babies may vomit blood or pass red blood in their stools. These severely affected babies usually do not thrive and are slowto gain weight in the first few months of life. Food allergies are thought to be a major factor in a significant number of babies diagnosed with gastric reflux disease. A small proportion of these babies develop an allergic inflammation of their gullet called 'eosinophilic oesophagitis' and this type of reflux disease needs to be supervised elimination of offending proteins in their diet.

Children with suspected foo hypersensitivity should be assessed by an experiences and interesed General Practitioner. Young babies with excessive irritability and crying should be assessed for the possibility of food hypersensitivity and reflux disease. In many cases diagnosis is as simple as trialling the elimination of potential food allergens in the diet of the mother in breat feed babies, or in the formula diet of bottle fed babies. This should be done in consultation with a doctor, child health nurse or paediatric dietician. In older children with severe reactions, a paediatric allergy specialist  should become involved. These allergy specialists can confirm the diagnosis of food sensitivity with skin prick testing and can provide accurate advice regarding further management based on the results. An elimination diet in children who have not being properly and accurately assessed by an experienced medical practioner is not advisable due to the risk of nutrient deficiency.

The likelyhood of resolution of food allergy depends on the food in question. The majority (85%) of children with lgE mediated allergy to milk, egg, wheat or soy, will lose their allergy by 3-5 years. Allergies to peanut, tree nuts, fish and shellfish are generally prolonged and can be life-long. Once a diagnosis of food allergy is established, strict elimination of the offending food is teh only treatment available. Referral to an experienced paediatric dietician is advised when an eliminiation diet is implemented to minimise the risk of nutrient deficiency. In teh next issue I will discuss life threatening allergic reactions to foods.

Dr. Roger Morris

MBBS (QLD) DCH, FRACGP