Food allergies and intolerances

You've read about them in magazines and probably know someone who suffers from one, but what are food allergies and intolerances, and how can they affect you?

Food intolerance is an umbrella term, which encompasses food allergies, enzyme defects like lactose intolerance, pharmacological reactions to foods and substances (such as headaches or facial flushing that result from histamine, serotonin and tyramine contained in cheese, coffee and pickled fish), and idiosyncratic responses to foods due to toxins they contain. Responses vary according to the individual, and how severe their reaction is to a particular food, but will generally include some form of rash. A food allergy is a specific kind of food intolerance, where the immune system reacts in an abnormal way to a food or food ingredient.

The way our immune system protects us against harmful, 'foreign' particles (called antigens) is by eliminating them from our body. This process of elimination can result in an immediate or a delayed allergic reaction. An immediate reaction is characterised by symptoms such as a runny nose, asthma, hot flushes, difficulty breathing, and swelling of the lips. This reaction is then mediated by the production of antibodies, which bind with the antigens and eliminate them from the body. Reactions vary in severity, and depend on how much of the offending food you've eaten. Unfortunately, it is difficult to know if you have a food allergy, until you actually have an allergic reaction, at which point you should consult a physician. Most likely, he or she will tell you to avoid the food and any related or trace elements of it. Delayed allergic reactions to food are more complex, and can take several hours to develop.