Is it a food allergy or an intolerance?

Is it a food allergy or an intolerance?

Make no mistake - food allergies can be deadly, and they're on the rise. The tiniest exposure to something you have a severe allergy to can be fatal so it's important to be aware of the signs of an allergic reaction.

There's a fundamental difference between food allergy and food intolerance. In allergy, your immune system (which normally helps you fight off infection) turns on your body and attacks it. This could be a local reaction - as in hay fever- or a 'generalised' allergic reaction, affecting your whole body. Food allergies are generalised because the food is absorbed into your system. The symptoms of food intolerance, on the other hand, are more likely to centre on your gut.

What causes an allergic reaction?

Some of the confusion between food allergy and food intolerance may come from the fact that there are also two kinds of generalised reactions: IgE and non-IgE reactions. IgE stands for immunoglobulin E - a type of antibody produced by your immune system. These react with specific 'antigens' - something your body recognises as an enemy.

It's only IgE-mediated reactions which result in life-threatening symptoms and IgE-mediated reactions come on within minutes or even seconds.

If you have a severe (IgE-mediated) food allergy, even the tiniest exposure to something you're allergic to can bring on this reaction. For instance, if food you're eating has been prepared on a surface where nuts were previously placed, even a trace of nut could trigger an allergic reaction in someone with a nut allergy.

Non-IgE-mediated reactions still involve your immune system, but the reaction can take many hours to come on. Non-IgE-mediated allergies may be debilitating, but the symptoms are often vague and harder to link to the trigger.

Recognising allergic reactions

The most extreme sort of allergic reaction is called anaphylaxis. Your immune system goes into overdrive and affects your whole body. It can lead to confusion, loss of consciousness and even death if not treated: the most serious consequences are much more common in small children. Symptoms come on rapidly - often within minutes - and progress with frightening speed. They include:

  • Wheezing and breathlessness (as your airways swell up and narrow). As the reaction progresses, your lips can turn blue because of lack of oxygen.
  • Swelling of your tongue, lips and throat (which can completely block your airways) and sometimes around your eyes, hands and feet.
  • An intensely itchy raised 'nettle rash'.
  • Palpitations.
  • Feeling light-headed or faint (as your blood pressure drops).
  • Feeling or being sick, cramping tummy pain and diarrhoea.
  • A feeling of 'impending doom'.

Teasing out the cause

If you ever have an anaphylactic reaction, you should always be referred to an allergy specialist. They may carry out blood tests for antibodies (from your immune system) to certain foods. They may also recommend patch tests. A tiny drop of liquid containing various foods you might be allergic to is placed on your skin; your skin is pricked, so the food can enter the skin; and any reaction on your skin (usually an itchy red area) signals an allergy. This should always be done in a clinic with full resuscitation equipment, because of the tiny risk of bringing on an anaphylactic reaction.

Staying safe

If you're at risk of an anaphylactic reaction, you'll need to keep an 'auto-injector' pen containing adrenaline (epinephrine) with you at all times, to be used at the first sign of anaphylaxis. Let friends and family know, and make sure they know where to find and how to use your pen in case you can't.

You should wear an allergy alert bracelet or similar, and should also be referred to a dietician. You'll need to learn how to avoid all contact with the food or foods you're allergic to, which can be a challenge if you're not cooking at home from scratch.

Many children grow out of allergy to eggs, wheat, milk and soya. But it's crucial not to reintroduce them into the diet except under strict medical supervision.

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Is it an intolerance?

Your immune system isn't involved in food intolerance, and on the whole the symptoms affect your gut. The main ones are feeling or being sick, diarrhoea, bloating and cramping tummy pain. However, sometimes exposure to food you're intolerant of can also leave you feeling tired or headachy.

Another important difference is that you can often tolerate a small amount of the food you're intolerant of. For instance, if you're lactose intolerant, you may be able to have a splash of milk in your tea but have severe cramp and diarrhoea if you have a whole glass of milk. It's never life-threatening to eat foods you're intolerant of, although it can cause miserable symptoms. Keeping foods that trigger your reaction to a minimum should control your symptoms.

Among the most common culprits are peanuts, other nuts, seeds (like sesame), egg, wheat flour, seafood and some fruits like strawberries and kiwis.

Coeliac disease isn't an allergy or intolerance - but people with coeliac must avoid any contact with gluten for life. But remember: don't cut out a wide range of foods without a dietician's advice - you could put yourself at risk of vitamin or mineral deficiency.

With thanks to My Weekly magazine, where this article was originally published.

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