When all Natalie Fine could see of her hospitalised six-month-old baby, Lucas, was a small pair of eyes peering out from head-to-toe bandaging, she couldn't help wondering what she had done wrong. She certainly didn't imagine soy-based formula -- recommended by her paediatrician after problems with a dairy-based formula -- could be the cause of his severe eczema, infected and requiring IV antibiotics.
"When I was told he had a soy allergy I felt terrible -- as if I had been poisoning him with the formula," says Fine. Lucas was also found to have a severe allergy to egg white, and his mother was warned that if he came in contact with egg he could have an anaphylactic reaction -- the most severe manifestation of allergy which can cause swelling of the throat, difficulty breathing, a fall in blood pressure and, in some cases, death.
Given the long list of foods that contain either egg white or soy, Fine was hesitant to give her son any food at first. "He lived on rice cereal and banana for quite a while," she says. Fine has since become more adventurous, but has become adept at reading the small print on food packaging, scanning for any mention of egg and soy.
Fine's family is just one of many in Australia experiencing first-hand the effects of the dramatic rise in the numbers of children developing food allergies.
This week the Australasian Society of Clinical Immunology and Allergy (ASCIA) found food allergies and other types of allergic disorders are rising fast in Australia.
The report, compiled by Access Economics, found these allergic disorders, including hayfever, asthma and others, already cost the nation $7.8 billion per year in absenteeism from work and other effects. But this is likely to rise sharply, as the 4.1 million Australians currently affected -- about one in five of the population -- is expected to soar to one in four by 2050.
While hayfever can be surprisingly debilitating in severe cases, it is not going to kill anyone. Food allergies, on the other hand, can be fatal -- as witnessed by the latest death just this week, when a 25-year-old woman collapsed in Brisbane after eating a dim sim containing seafood.
But the biggest rise in food allergies is being seen not in adults but in children under five, as shown by data published in the October issue of the Journal of Allergy and Clinical Immunology (2007;120:878-84). The study found a 5 1/2-fold increase in the rate of Australian hospital admissions between 1994 and 2005 for food-related anaphylaxis in the under-fives -- a much greater rise than in any other age group. Shortages of allergy specialists also mean it can take months for parents to get an appointment.
Similar trends have been observed in the UK and US, but experts are at a loss to explain what is causing it.
"We have more theories and questions than answers," says Raymond Mullins, an allergy specialist in Canberra and president-elect of ASCIA. "It has something to do with our westernised lifestyle: you just don't see it in developing countries."
The most common causes of food allergy in children are cow's milk, egg, peanuts, tree nuts and sesame, he says.
Food allergy has a significant effect on quality of life for children and their parents -- similar to the effect of insulin-dependent diabetes in a child, says Mullins. The stress comes from anxiety about the child having a reaction, as well as the need for preparation of special meals, planning of outings, and liaison with other caregivers such as teachers, he says.
In the Medical Journal of Australia in June (2007;186:618-21), Mullins reported a 12-fold increase in demand for consultations related to food allergies in children over 12 in his practice. "In the same way research has helped us identify risk factors to help reduce the risk of sudden infant death and heart disease, we need large-scale epidemiological studies to work out why allergy is becoming more common and how we can prevent it."
One strategy shown not to be effective for cutting the risk of food allergy is avoiding allergenic foods during pregnancy. However, many women still think cutting out peanuts and the like at this time will help.
Parents are not the only ones who could be wrong on this issue. The UK Department of Health has been advising women to avoid peanuts in pregnancy if there is a family history of allergy, but a House of Lords report on September 26 said the advice should be withdrawn immediately due to a lack of evidence. In Australia such elimination diets have not been officially recommended, and ASCIA's guidelines advised against them three years ago, citing a lack of evidence and the risk of smaller babies if mothers undertook elimination diets.
Despite the guidelines, many of Mullins's patients do exclude potentially allergenic foods during pregnancy, probably based on information from the media, friends, the internet and community mythology, he says.
However, some academics are worried that excluding foods during pregnancy may even make allergy more likely in the child.
Associate professor Mimi Tang, head of Melbourne's Royal Children's Hospital department of immunology, says although we don't understand whether sensitisation to foods occurs in pregnancy, the body must be exposed to a food for the immune system to become tolerant to it -- so avoidance is unlikely to be the right strategy.
Consistent with this line of thinking is new evidence that delaying introduction of solid foods beyond seven months in a baby may increase the risk of allergy, she says. The question of when to introduce solids is a whole other area of confusion and conflicting information -- as Mullins found when he compared the advice on this issue from sources such as state health departments and infant nutrition companies.
While many other sources recommend delaying introduction of potentially allergenic foods, such as egg and dairy, until 12 months of age if there is a family history of allergy, ASCIA advises there is no evidence that waiting until the child is more than six months old to introduce these foods will reduce the risk of allergy in the long term.
There is also no good evidence that restricting foods during breastfeeding will reduce the risk of food allergy in the child.
"There has been a perception that avoidance is a good thing if you have allergies, but I think this advice will change," he says. Parents should keep an eye on the ASCIA website (www.allergy.org.au) for up-to-date advice that is evidence-based, says Mullins.
The theory that early exposure to an allergen actually helps a child's immune system become tolerant is being tested currently by the LEAP (Learning Early About Peanut allergy) study in the UK.
The researchers will compare the rate of peanut allergy at the age of five years in children who were exposed repeatedly to peanut and in those who avoided it.
Tang is studying another strategy, based on the theory that the food allergy epidemic is related to a reduction in "good" bacteria in some children's gastrointestinal systems -- the "hygiene hypothesis". Proponents of this theory suggest we have become too clean for our own good and children's immune systems are suffering because of a lack of good bacteria. The imbalance possibly causes the child's immune system to react inappropriately to certain foods.
"There is some evidence that children who grew up on farms have lower rates of allergy -- particularly if they were exposed to farm animals and drank unpasteurised cow's milk," Tang says. "And we know kids with allergy problems have lower numbers of good bacteria like bifidobacteria and lactobacilli, and higher numbers of pathogenic bacteria, those that can cause disease, in their gut flora than healthy children."
At birth, babies' gastrointestinal systems are sterile, but bacteria soon make themselves at home. "For children with allergy problems the imbalance in good versus harmful bacteria occurs within the first weeks or months of life," says Tang.
Studies where probiotics (good bacteria) have been taken by mothers in the last weeks of pregnancy, and then by their babies in the first months of life, have shown a reduction in allergy symptoms for up to eight years of age. Tang is currently conducting a study to see whether giving a probiotic to the mother in the last four weeks of pregnancy is sufficient to gain the benefit.
Until more of our questions about allergy are answered by research, the following measures are the best advice for reducing the risk of allergy in children with a family history, says Tang: do not smoke during pregnancy or around children; where possible, breastfeed exclusively for the first four to six months of life (if this is not possible, a partially hydrolysed cow's milk formula may be used if the child does not have a cow's milk allergy); and delay the introduction of solid foods until four to six months.
