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Text 1: Allergic to eating

Lucy Smith was strolling through Canberra last July. Within moments she couldn’t stand, gripped by pain so severe she feared she would pass out – the first sign of paralysing diarrhoea. This dramatic episode turned out to be caused by a newly-acquired food allergy – to red meat. Food allergies affect one per cent of the adult population of Australia. Most don’t hit with the same force as Lucy’s, but the physical and mental impact can nonetheless turn a person’s life upside down, and may even be life-threatening. Lucy deduced that she was allergic to red meat, one of the less common allergenic foodstuffs. Only after several further attacks of varying severity, was her suspicion eventually confirmed by a specialist.

An allergy, according to immunologists, is the immune system over-reacting to a substance that would ordinarily be considered benign. However the term ‘allergy’ is used more loosely by the general public. People say they are allergic to a substance because it brings about some kind of adverse reaction in their bodies, some of which can be severe and may resemble true allergic reactions, but unless the immune system itself is directly involved, experts categorise it as ‘intolerance’. Constant sneezing, itchy eyes or throat and inner ears, asthma, rashes, and diarrhoea can all be signs of food allergies. Intolerance can bring on similar warning signs as well as things such as headaches, bloating, and general lethargy. Over time, some allergy sufferers lose weight because there are so few foods they can eat. Of course the social implications are huge too – eating is a major social event.

To diagnose a food allergy, immunologists use a ‘skin-prick test’ in which a drop of a commercially extracted allergen is placed on the skin and the first couple of skin layers are pricked with a lancet. If a person is allergic, the immune system is stimulated sufficiently to produce a mosquito bite-like bump within fifteen minutes. This testing method is, however, somewhat unreliable in detecting intolerances, because, while not fully understood, they operate via a different biological mechanism possibly involving chemicals in food irritating nerve endings in the body. They are generally diagnosed by following an exclusion diet in which suspect foods are gradually reintroduced and their effects monitored.

According to paediatric immunology specialist Dr Velencia Soutter, around six to eight per cent of babies are affected by allergy. While most children will outgrow them, some actually grow into them. The mechanisms that provoke an allergy remain a grey area. Soutter says: ‘It’s like throwing a match into a fireworks factory. Hit the right place and you set off a chain reaction. Miss it and the match just fizzles out. That difference between lighting up or fizzling out isn’t well understood.’

Broadly speaking, Dr Soutter says the ideal recipe for a food allergy is to be born of allergic parents and then to have a high exposure to an allergenic foodstuff. But there are so many exceptions to this rule that other forces are clearly at work, and who’s to say what ‘high’ exposure is anyway? In contrast, the so-called hygiene hypothesis suggests too low an exposure to allergens is to blame. The idea is that today’s clean environments leave our immune systems with too little to do, encouraging them to turn on the wrong culprits. Clearly, the field of immunology has only just scratched the surface of understanding.

Interesting flakes of information are gradually being peeled off that surface, however. There is evidence that allergens can be transferred through a mother’s breast milk to her child, and possibly also through the placenta. Since the immaturity of babies’ immune systems might make them more vulnerable to an inherited allergic tendency, women in allergic families could be advised to avoid certain foods during pregnancy and breastfeeding. It is possible, though, that some allergies or intolerances are purely imaginary and this can also have consequences for children. One US study found that parents sometimes avoided foods to which they erroneously believed their children were allergic, occasionally leaving the children severely underfed.

In Australia, the number of people with genuine and severe allergies is growing. Some doctors speculate whether the increased amount of new chemicals in the environment and in food is perhaps damaging immune systems − making them more prone to react adversely. Much more research needs to be done to provide evidence for that hypothesis. Anecdotally though, some experts say that staying off processed foods resolves the problem in a significant number of cases. Dr Soutter speculates that a rise in peanut allergy cases makes up the bulk of the increase in food allergies. Greater exposure has probably allowed more peanut allergies to flourish, she thinks. Peanut consumption per capita is rising. It’s a common ingredient in Asian and vegetarian dishes, which have grown in popularity, and the diet-conscious population is increasingly turning to nuts as a source of healthy fats.