Mukesh Haikerwal knows all too well the danger of a food allergy. It was 14 years ago that the Melbourne GP and former president of the Australian Medical Association first recognised symptoms of anaphylaxis in his then one-year-old son.
''As a father it was horrendous,'' he says. ''You have this child that won't settle and then you take off his top and he was beetroot red. I knew straight away it was an anaphylactic reaction.''
Convincing others to take his son's nut allergy seriously was not as straightforward.
''When he started in kindergarten and primary school it became very difficult. A severe allergy is different to an intolerance; it is not just a bit of a rash or a bit of an itch, it is actually life-threatening.''
When it comes to food allergies, Australia could well be the world capital, with an estimated one in 10 children affected. However, despite the number of preschoolers with potentially life-threatening food allergies increasing fivefold since 1990, the medical profession is at a loss to explain why.
Looking for answers
Paediatric gastroenterologist and allergy specialist Professor Katie Allen and her colleagues at Melbourne's Royal Children's Hospital hope to find an answer.
After recruiting 5000 one-year-old children for a study of the problem three years ago, they found 10 per cent had an allergic reaction to a food challenge. The team is now testing the children at age four and will expose them to the foods again at age six.
''So far, all we know is that it has something to do with modern lifestyles,'' Allen says.
Among the hypotheses are inadequate exposure to vitamin D, parasites, the age at which foods are introduced and the ''hygiene hypothesis''.
''Having lots of different diverse bugs in the intestine helps the system decide what we are eating is safe and what is dangerous,'' Allen explains.
What can baby eat?
Advice on the age to introduce certain foods has also changed. For the past decade, parents were advised to delay potentially allergenic foods until after their child turned one or two. Recent studies, however, have indicated that delaying the introduction of troublesome foods might increase the risk of an allergy developing.
Last year, Allen and her team found children who were not introduced to eggs until after their first birthday were up to five times more likely to develop an egg allergy. Infants who were introduced to egg between four and six months of age were least likely to develop an egg allergy.
''We are thinking now that there is a window of opportunity and that the intestine is ready for foods at certain stages,'' Allen says.
Who and what
The most common food allergens are peanuts, tree nuts (such as hazelnuts, cashews, pine nuts and macadamias), fish, shellfish, cow's milk, soy, egg and wheat.
Most allergies develop in childhood, although in rare cases adults can develop an allergy. While more boys develop allergies in childhood than girls, women are more likely to develop allergies later in life, something doctors attribute to hormonal changes such as when a woman becomes pregnant.
While 80 per cent of children grow out of an allergy to eggs, wheat or dairy, it is the nut and seafood allergies that are of greater concern. They are the most likely to trigger anaphylaxis and are also the most likely to persist as the child gets older.
Agents of intolerance?
What is far more likely to develop in adulthood is an intolerance to a particular food. Nutritionist Emma Sutherland says it is important to differentiate between an allergic reaction and an intolerance.
''An allergy is a reaction that produces an immune-system response and it generally means you can never eat that food,'' she says. ''With an intolerance, the symptoms are much more insidious, people could just feel tired and bloated or get a lot of headaches or colds, the kind of things you can put down to a host of other reasons.''
Sutherland advises those concerned about food intolerances take a blood test.
''If you only work on assumptions then you could be avoiding some foods that you think are causing the problem and still eating the ones that actually are.''
Those concerned about allergies also have a simple solution: a skin-prick test from an immunologist.
''Allergies are in response to a certain protein,'' Allen says. ''Food allergies have a bad reputation and people are seen as fussy but if someone has a positive skin-prick test, it means they are at risk of a more severe reaction.''
Symptoms of an allergic response include swelling on the face, hives, vomiting, coughing, wheezing and breathing difficulties.
The reaction is closely linked in time to a certain food, from within minutes up to an hour.
Sufferers should see their GP for a referral to an allergy specialist.
Symptoms of an intolerance can include bloating, headaches, stomach pains and even excessive tiredness.
Those who suspect an intolerance can try eliminating a single food for a week and then reintroducing it. This is not advised for suspected allergies.