Imagine you have a happy and healthy young baby. The first time you try to give them some cow's milk - less than a mouthful - their eyes swell up so they can't even see, their lips swell, a blotchy rash appears and they begin coughing and struggling to breathe. This type of food allergy, which can cause a life threatening anaphylactic reaction, is unfortunately becoming more common.
Food allergies are a modern phenomenon. Virtually unheard of until recently, the number of cases has grown by more than 500 per cent in the last 10-15 years so we now think that up to one in ten children of 12 months of age are affected.
And food allergies are dangerous. In severe cases, patients can go into anaphylaxis within seconds of even minor contact with some foods.
Food allergies are abnormal immune reactions to foods and can vary widely. Although any food can potentially cause an allergic reaction, more than 90 per cent of childhood food allergies are to common foods such as hen's eggs, cow's milk, soy, peanuts, tree nuts, wheat, fish and shellfish.
In general, allergies for egg, milk, soy and wheat are transient, meaning children will grow out of the allergy with tolerance in most cases developing by school age. But allergies to peanuts, tree nuts and shellfish tend to be more persistent and life-long disorders.
Allergic reactions are usually quite obvious with immediate symptoms ranging from mild rashes to life threatening reactions. The typical allergy rash is caused by histamine release and appears as raised pale welts surrounded by redness - sometimes referred to as hives.
If swelling affects the throat and makes breathing difficult, then the reaction is more serious. Even more subtle signs such as voice hoarseness and coughing can suggest an anaphylactic reaction.
Massive histamine release during anaphylaxis can cause a dangerous drop in blood pressure, with patients appearing pale and some may even lose consciousness. As with obstructed breathing, this is very serious and can be fatal.
Allergies are the result of incorrect decisions by the immune system. Although we depend on proteins and other nutrients from the external environment for our survival, our immune systems must quickly learn whether these are safe or not, and sometimes it gets it wrong. Most of these critical decisions have to be made during infancy, when the immune system is still immature.
Researchers around the world, including in Perth through The Kids Research Institute Australia, are playing catch up as they try to understand what is causing the big increase in food allergies.
Professor Susan Prescott, who leads research into food allergies at the Institute, says many changes in our modern environment are likely to be causing this, but one of the leading candidates appears to be the disruption of the normal healthy bacteria that are so important for the developing immune system.
This is partly the result of cleaner environments and partly due to the western dietary patterns that promotes less healthy gut bacteria. The resulting disruption of healthy gut biodiversity appears to be having a negative impact on the development of some children's immune systems.
Allergy tests are typically used to confirm a suspected allergy, but they are also used to exclude an allergy to certain foods and other potential allergens.
The two main methods are either a blood test or an allergen skin prick test. Both tests measure allergic antibodies to specific allergens such as foods, pollens, dust mites and insect venom. The most conclusive way to show or exclude an allergy is to have direct exposure under controlled, supervised conditions, but this kind of test is usually unnecessary where there is a history of recent, severe reactions to specific foods.
Once a trigger is identified, plans can be put in place to avoid or minimise contact. For some allergens, some contact is unavoidable so your doctor will also set out a clear treatment plan to follow when symptoms are triggered. Having well prepared plans is particularly important for potentially life threatening conditions such as anaphylaxis.
In the longer term, immunotherapy - gradually giving increasing doses of allergen over an extended period - is currently the only established method of reducing a reaction to an allergen.
For food allergies there have been some reports of using this approach successfully to 'cure' patients with anaphylactic reactions to egg, milk and peanuts. However, side effects are common and there is a high risk of reactions, especially during the build-up phase. This approach remains a research tool at this time, but does offer future hope for many people with food allergy.
Professor Prescott has written two books which are available from UWA Publishing. All proceeds go towards funding allergy research.