Surgery notes
with Dr Graham Easton

15 October 2007

Allergies: how your GP can help

There’s been a marked increase in allergic diseases over the past few decades - about a third of the UK population is now affected at some point in their lives - but the NHS has struggled to keep up. There is little medical training in the UK covering allergies, allergy tests are hard to come by and we’re desperately short of specialist allergy services.

So how can you get the best from what the NHS can offer?

Know what you mean by 'allergy'

People tend to use the word allergy to describe any unpleasant reaction, whether it's to food, medication, insect stings and so on. But the word allergy means something more specific - it describes the body's reaction when your immune system comes into contact with a trigger substance (an allergen) that it recognises and then produces a particular type of antibody called immunoglobulin E (IgE).

This kicks off a rapid release of other chemicals - including histamine - that produce the unpleasant symptoms associated with allergy. Extreme reactions (anaphylaxis) can cause life-threatening collapse.

Some of the common conditions where allergy can play a part include asthma, hay fever, conjunctivitis, eczema (particularly young children) and food allergy.

Food allergy or intolerance?

I meet lots of patients who think they've got a food allergy. Some do, but most will have a food intolerance, which is not the same at all.

Allergy specialist Jonathan Brostoff, professor of allergy and environmental health at King’s College London, told me: "They're completely different. Food allergy is an acute (rapid) reaction involving IgE, mast cells (like microscopic hand grenades containing histamine) and an allergen. Food intolerance is delayed by up to three days, mostly the next day, and the mechanism is unknown. It's probably mediated by lymphocytes (white cells).

If someone has an acute food allergy, they'll know the cause and be able to avoid it. That's the crucial difference."

Allergy homework

Typical symptoms might suggest you have an allergy, but they can all be caused by non-allergic conditions, too. It's vital to get the correct diagnosis so you know what you're dealing with, what to avoid and what treatments might help.

I'd recommend making an appointment to see your GP, but in the meantime be clear about what your main symptoms are and how they're affecting your life.

• Do they stop you doing things?
• When and where do you tend to develop these symptoms? For hay fever or asthma for example, are they worse at a particular time of year or day? Do you tend to only get the symptoms when you're at work, outside, or at home? A formal symptom diary can help.
• Think about whether any of your relatives have allergies - of any sort. Many allergies run in families, particularly asthma, hay fever and eczema (the so-called 'atopic' conditions).
• Finally, make a note of what self-help remedies you've tried and whether or not they help.

Some people exclude a particular food or food type from their diet for a set time to see whether their symptoms improve. It makes perfect sense to avoid obvious triggers if they seem to cause allergic symptoms, but if you're just fishing for potential foods to which you're intolerant, it's best to get professional advice (for example, from a dietitian) before putting yourself at risk of dietary deficiency through an exclusion diet.

Seeing your GP

Between you and your doctor, you should be able to decide if it's an allergic condition. The great thing about going to your GP is that he or she will also be thinking about the whole range of other non-allergic conditions that could be causing similar symptoms, and may want to examine you or arrange further tests with this in mind.

Allergy tests

You may need allergy testing to find out which specific triggers are behind your symptoms. This is particularly important if you've had more severe reactions, or if there's any confusion about whether it's a true allergy or something else. The main allergy tests are:

• Skin prick tests (for IgE sensitivity to common triggers). Simple, quick test, done in GP surgery or hospital clinic by specially trained doctors or nurses. Can give useful information about all types of allergy, including things you inhale or eat.
• Blood tests (tests for IgE antibodies to specific triggers). Measure how strong an allergic response is - the higher the level of IgE antibody to the trigger, the more likely you are to be allergic. Useful when someone's had a severe reaction and to screen for a range of potential food allergens, and in people with severe eczema when skin testing is impractical. A positive result doesn't always mean you're allergic. Blood sample can be taken in GP surgery, sent to your local hospital laboratory, and results should be available in one to two weeks.
• Skin patch tests (for suspected contact allergies on the skin). Applied to the skin for 48 hours. Results need special analysis so tests usually carried out in hospital dermatology departments. May be useful in people with hand eczema where contact allergy to foods might be a cause.

Are blood tests useful for diagnosing food allergy or intolerance?

Professor Brostoff says tests for acute food allergy are reliable and widespread, but there's no reliable and universally accepted test for food intolerance because the mechanism of the reaction is not known.

"The immunoglobulin G (IgG) test shows the person has met and recognised the allergen but doesn't necessarily mean the patient is allergic to that allergen," he says. He thinks a standard elimination diet can be more useful in some conditions - irritable bowel syndrome, for example.

What's the treatment?

For simple cases, with a proper exploration of your symptoms and any necessary further tests, your GP should be able to advise you on the most effective measures to deal with your allergy.

These will mainly involve avoiding the problem allergen(s), but is also likely to include medications such as antihistamines or steroids to dampen down your immune system's over-reaction.

For more complex or severe cases, you have to hope you can be referred to one of the six major UK allergy centres.

As Professor Brostoff says: "We have the smallest number of allergists per head of population of any country in Europe and there are fewer than ten doctors in the country currently being trained to become specialist allergists."

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