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Ever Wondered About... Allergies?

Updated Wednesday, 27th April 2005

The scientific background to common food allergies

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Just imagine what life would be like if you had to scrutinise the ingredients of everything you took down from the supermarket shelves. If eating out at a restaurant was literally a matter of life and death. Or if your toddler’s well-being depended on your keeping the house meticulously clean and carrying a syringe with you wherever you go. These are all part of day-to-day life for people living with severe food allergies.

Did you know …?
In the UK, about 20% of adults believe themselves to be allergic to a certain food, but only about 1.4% have scientifically proven allergies.

In many western countries, there has been an inexorable increase in the prevalence of food allergy, alongside other allergic conditions.

In reactions such as peanut allergy, the body’s own defence mechanism, the immune system, turns against an otherwise harmless foodstuff.

The most common cause of wheat allergy is the protein gluten, which gives bread its characteristic texture.

Allergies and Science
A lot more people think they have allergies than the science would suggest. Food allergies are often confused with food intolerance – for instance when someone’s digestive system is short of a certain enzyme, making it difficult to digest some foods. Food allergies can also be confused with food aversion, where the unpleasant effects of eating a food are induced by psychological factors. True allergies engage the body’s immune system: they can be detected by repeatable, scientific tests which show an immune reaction.

Did you know …?
About five Britons die of a food allergy every year.

An inexorable increase?
Allergic reactions probably evolved to help protect against childhood infections, which are particularly likely to occur in large families and unhygienic conditions. But perversely, in our nice clean modern homes where there is less infection to cope with, allergic reactions seem to cause damage by producing exaggerated reactions to harmless dust mites, food or pollen. Put very simply, the human immune system has two main branches. One side is responsible for fighting infections, the other for allergic reaction. This leads to one of the great intriguing questions of contemporary immunology. By under-using one side of our immune systems, could we be unwittingly provoking the other side to turn against ourselves?

Did you know …?
There has been a doubling or trebling of childhood allergenic asthma since the early 20th Century.

Peanut allergy
Peanut allergy could be described as the body’s "friendly fire". The immune system is a bit like a miniature army, defending your body against invading bacteria, viruses and parasites. It has battalions of specialised cells patrolling the body, seeking out infection. These cells use batteries of chemicals, to communicate with each other and to kill off invaders. Peanut allergy starts without your even knowing it, when your immune system interprets a component of peanuts as a sign of enemy invasion. The next time you eat a peanut, the immune system leaps into action, mobilising all its forces, sometimes with fatal results. The process is called anaphylaxis:

  • Anaphylaxis takes place in specialised cells called mast cells.
  • Inside, the cell is crammed with a cocktail of chemicals including histamine
  • The antenna-like molecules on the surface are immunoglobin E (IgE)
  • Proteins from a peanut bind to the IgE
  • This causes the release of histamine, which in turn causes swelling, sneezing, vomiting, spasm of the lungs, fall in blood pressure and sometimes, tragically, even death.

Did you know …?
Taxonomically speaking, peanuts are not nuts. They are legumes.

Peanuts grow underground. They are most closely related to peas, beans and lentils and not at all closely related to other nuts, which grow on trees. This could matter to peanut allergy sufferers: closely related species are more likely to contain similar proteins. It also matters to biologists, who devote a lot of time and effort to classifying living things. The study of classification, or taxonomy, can sometimes give an insight into the degree of evolutionary relationship. This in turn can help answer some of the biggest evolutionary questions of our time, such as solving some of the mysteries of the dinosaurs.

Did you know … ?
The peanut plant is a native of South America which is now grown in five continents.

Wheat allergy
If bread is the staff of life, then proteins are its most fundamental building blocks. Proteins are the complex 3-dimensional molecules around which bread and bodies alike are built. People with wheat allergies are usually allergic to a protein called gluten. This strong, elastic protein is responsible for bread’s light, airy structure. When water is added to flour, two proteins, gliadin and glutenin, hydrate to form gluten. Kneading the dough helps to spread the gluten network. But for the small minority of people who are allergic to gluten, total abstinence is the only answer.

Did you know …?
Truly wheat-intolerant patients must avoid sausages and beer as well cakes, malt bread, pasta, sauces … and many more.

If you are allergic to a food, total abstinence is often the only option. And if it happens to be a gluten allergy, you’ll be surprised how many foods contain the stuff! But it’s crucial to be sure that you genuinely do have an allergy, and an elimination diet should always be supervised by a qualified nutritionist. Human beings evolved to eat a broad mixed diet of proteins, carbohydrates, fats, fibre, vitamins and minerals in balanced combination. And we tamper with that natural balance of nutrients at our peril.

Did you know …?
Turning wheat into beer was one of mankind’s earliest biotech industries.

 

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