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Food Hypersensitivity In Children

27 Jan 2006 7:46 PM - Dr Roger Morris

‘Food hypersensitivity’ is defined as an adverse reaction to a food protein that results from an 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 the 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, 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 (IgE mediated) occurring within 30min to 1 hour after ingestion, or they can be delayed (usually non-IgE mediated) where symptoms develop several hours to days after ingestion of the food. The rapidly occurring allergic reactions can be the most dangerous and usually involved reactions on the skin (hives, itch, red patches) and intestines (vomiting, diarrhoea, abdominal pains). Severe IgE mediated allergic reactions can lead to potentially fatal effects in the airways (wheezing, constriction of upper airways, severe tongue/mouth swelling) and circulation (severely lower blood pressure and circulatory shock). This severe end of the spectrum is known as ‘anaphylaxis’ and can be rapidly fatal if not treated aggressively and in a short time after occurrence. In children, anaphylaxis occurs most commonly with exposure 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 seem 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 slow to 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 treated by supervised elimination of offending proteins in their diet.

Children with suspected food hypersensitivity should be assessed by an experienced and interested 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 breast fed 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 been properly and accurately assessed by an experienced medical practitioner is not advisable due to the risk of nutrient deficiency.

The likelihood of resolution of food allergy depends on the food in question. The majority (85%) of children with IgE 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 the only treatment available. Referral to an experienced paediatric dietician is advised when an elimination diet is implemented to minimise the risk of nutrient deficiency. In the next issue I will discuss life threatening allergic reactions to foods.