TOMORROW, Toorak schoolboy Monte Kellett will take the walnut challenge.
Pediatricians will feed the seven-year-old mashed walnuts mixed with yoghurt, in the safety of the Royal Children's Hospital, to gauge his body's response.
The previous time Monte ate walnuts they were in a small wedge of carrot cake his mother Jude picked up from a city cafe. Minutes after eating a "smidgin" of it, hives covered Monte's body and head, he itched furiously and laboured to breathe. Mrs Kellett rushed her son to a GP for a shot of antihistamine, and the symptoms settled after two hours.
A similar response at tomorrow's test means Monte can add walnuts to his already extensive list of allergens, which includes peanuts, cashews, dust mites, pollen and grass.
According to the Australasian Society of Clinical Immunology and Allergy, one in three Australians will develop an allergy — double the rate of 25 years ago.
Food allergies in infants have soared fivefold between 1993 and 2005.
That's the assessment of immunology and allergy researchers based on hospital admissions for serious allergy complaints such as anaphylaxis — a life-threatening condition induced by allergens as ordinarily innocuous as peanuts and other foods.
Associate professor Jo Douglass, head of The Alfred's allergy and asthma service and a researcher at Monash University, said the trend was entrenched. "It's been quite an increase; 2½ times over the past three decades.
"Rates of asthma have doubled in children, rates of hay fever have increased three to five times — that's in Australia and internationally."
But experts are baffled as to why allergies have become more prevalent, citing changes in our environment and diet as possible explanations. That allergies are especially troubling in developed countries, such as Australia, Britain and the US, means environment and lifestyle may be factors.
"We live in houses with pets and carpets so indoor allergens are different (from developing countries)," said Professor Douglass.
"The pollution is different; poorer countries tend to have more coal or wood-based pollution whereas ours is more based on petrochemicals.
"And the diet is very different, and we have much more exposure to antibiotics.
"Food allergies in children has become a major issue.
"In very young children the rise has been towards food allergies and it's remarkable. We're talking about a rise of up to four to five times."
Even trace amounts of peanut or micrograms of bee venom can set off anaphylaxis in sensitive people.
A reaction is triggered when the body creates allergic antibodies, called immunoglobulin E or IgE, in response to the allergen. These allergic antibodies can trigger a cascade of harmful immune reactions by attaching to other cells that start releasing histamines.
"Because (an allergic person's) body produces these allergic antibodies, there is a harmful … response to substances that would otherwise be harmless," Professor Douglass said.
There are no cures and no vaccines for allergies — only preventive measures.
Professor Douglass said the best treatment was avoidance — a task easier said than done.
It is easy to avoid penicillin, but almost impossible to avoid pollen. Food allergies lie somewhere in between, depending on how prevalent the food is in kitchens, restaurants and food manufacturing.
In some cases, doctors have learnt to "switch off" allergies through desensitisation.
By introducing tiny amounts of allergen over a long period, the body can learn not to produce a harmful immune reaction.
It can take years to complete and, so far, has only worked with bee venom. Similar tests using food in the US were stopped after too many participants went into anaphylactic shock.
The goal of allergy researchers is a treatment that switches the allergy off without maintaining immunotherapy treatments such as desensitisation.
The head of allergy research at the Murdoch Children's Research Institute, Mimi Tang, said a cure could be anything from five to 20 years away. "But every day we're getting closer," she said.