A guide to self-diagnosis of allergy or intolerance to food

Dr Harry Morrow-Brown has practised as an allergist for over 50 years but despite the best efforts of a dedicated few, he believes that the provision for investigation into allergy in the UK remains ‘the most inadequate in Europe’.
For those patients who are unable to access expert help he has some suggestions as to how they might try to understand their own condition and ‘diagnose’ their own allergies or intolerances. However, we must make it clear that these are only suggestions and neither Foods Matter nor Dr Morrow-Brown can assume any liability for their use.

In Britain today allergies are suppressed with drugs as far as possible, doctors know little or nothing about them, and provision for investigation is the most inadequate in Europe. But there is nothing to prevent a patient trying to understand their allergies and attempt a self-diagnosis, so the following explanations and information may be helpful.

Allergies - what are they?
An allergic person reacts to eating, touching, or inhaling a substance that everyone else can tolerate without the slightest adverse effect. This substance is called ‘the allergen’.

People with a tendency to be allergic, usually because allergy runs in the family, often develop special IgE antibodies in their blood directed against common allergens such as pollen or dust mites. These antibodies can be detected in the blood, or by skin testing, but their presence means only that the person has an allergic tendency without necessarily having any symptoms. Positive skin and blood test results in apparently normal people can, therefore, be misleading. People who develop these antibodies are referred to as ‘atopic’ subjects, and they are predisposed to develop allergic diseases.

Allergic reactions
IgE antibodies in greater amounts in the blood, plus very positive skin tests, associated with an allergic problem of some sort means that very tiny amounts of the allergen will cause a sudden reaction.
Allergic reactions usually affect only one organ, such as the nose in hay fever, the chest in asthma, the skin in eczema, and blood vessels and the gut in anaphylaxis. Both nose and chest are often affected because they are both part of the respiratory system.

The holistic diagram above shows how different parts of the body can be involved. For example babies often develop eczema, which subsides after a few years only to be replaced by asthma and/or allergic rhinitis which may be a life sentence. This sequence of events is called the ‘allergic march’.
To understand allergic reactions it is helpful to regard the ‘allergen’ as a key that will turn on the reaction, but only if it fits the ‘lock’ in the body system affected. The key, the allergen, must cause the same reaction every time it is turned.

Patients often jump to conclusions on the basis of only one episode where cause and effect seem convincingly related. One episode can easily be due to chance, and twice is suggestive, but only three times or more is convincing.

The allergen may be present only in summer, or constantly or occasionally present in the environment or in food. This concept emphasises the importance of establishing a repeatable cause/effect relationship, which can vary from an obvious immediate reaction to a slow reaction the following day or even later, as in food intolerance. The longer the interval between cause and effect the more difficult it will be to establish a repeatable convincing relationship between cause and effect, key and lock.

The objective is to identify the allergen so that it can be avoided and allergic reactions prevented. I would emphasise that food intolerance is quite different from allergy because both skin and blood tests are negative, and large amounts of food are required to set off a reaction, which is very often delayed.

Anaphylactic shock
Anaphylactic shock is the most severe form of allergy because it can be life-threatening. The cause could be an injection of venom from a wasp or bee sting, a doctor injecting a drug unaware that the patient is allergic to it, or, more frequently, eating food including nuts or another food to which the person is allergic.

This is the most extreme and dangerous sort of allergic reaction involving blood vessels all over the body so it is really important to find the allergen and avoid it if possible. Usual allergens are peanuts, tree nuts, eggs, milk, wheat and fish, insect stings, and drugs such as penicillin and muscle relaxants. A reaction usually requires treatment at Accident and Emergency, but investigation after recovery must be arranged.

Careful interrogation regarding what was eaten within an hour or two of the incident is essential, and blood and skin testing at a centre of excellence are equally essential.

Insect stings can be fatal, but the patient can be desensitised by a course of injections. These are available at some centres, but may be difficult to find. Your doctor should be able to refer you.

Failure to pin-point the cause of anaphylaxis by blood and skin testing is not uncommon, so these patients have to be aware of all possible causes and carry an auto-injector syringe containing adrenaline at all times to treat an attack at once. Joining the Anaphylaxis Campaign (01252 542029 www.anaphylaxis.org.uk) is essential to keep up to date with developments and be aware of the risks.

Seasonal allergies
The time of year when hay fever or asthma occurs often indicates the cause. For example hay fever in March, April and May is due to tree pollen, especially birch. This is followed by the grass pollen, the commonest cause of hay fever, starting in early June and often continuing into August – it is usually worst during Wimbledon tennis tournament! Symptoms are limited to the nose, eyes, and sometimes chest, are worst outside, in the morning and evening, and are relieved by rain.

For the first time since 1986 injections (Pollenex) or self-administered daily drops under the tongue (Gravax) are available through the NHS. These treatments aim to immunise patients against pollens when drug treatments are ineffective.

Most doctors are unaware that these treatments are now available, and primary care trusts are reluctant to allow them because of expense, so you should ask your doctor for them as soon as possible so as to get started well before the next season.

For important occasions, such as examinations and weddings, severe hay fever can be completely abolished by taking steroid tablets for a few days. There are no side-effects from only a few days steroid treatment.

From July onwards the main seasonal causes of hay fever and asthma are mould spores and yeasts, which come into the air in billions during damp or wet weather. Drugs are the only available treatment in this country, as preventive vaccines are not available. Symptoms are often linked with the weather.

Seasonal allergies occur every year around the same dates, therefore awareness of the season may enable the patient to tactfully help the doctor to recognise the most likely allergens. Drug treatment is most effective if started a week or more before the date when symptoms usually begin, and is continued regularly every day until the end of the season.

Environmental allergies
Asthma, rhinitis (perennial hay fever) and some cases of eczema are due to a continuous reaction to something always present in the environment at home or at work.

For example, allergy to animals may be obvious when sneezing, itchy eyes or wheezing occur almost immediately on contact with an animal. The constant presence of a pet may cause constant symptoms. The best evidence is when holidays coincide with improvement, followed by prompt relapse on return home. Sometimes picking up the pet on the way back from the airport will cause a return of the rhinitis, asthma or eczema before reaching home. In such a situation a difficult choice may have to be made.

Dust mites
The commonest environmental allergen is not pets but the ubiquitous dust mite which cannot survive in dry conditions in countries such as Switzerland. This important allergen, the commonest in this country, is contained in the mite faeces which are present in every bed, where the patient provides the humidity the mites need.

In all other western countries immunising injections or drops under the tongue are used to desensitise against mites. In the UK desensitising injections are permitted to prevent hay fever, which is never fatal, but forbidden for asthma which has considerable mortality.

In Britain all we can do is to try to control the mite infestation which is present in every home to greater or lesser extent. All methods of mite control or removal were recently condemned as a waste of money and effort, based on a purely statistical survey. The fallacies in this misguided investigation were explored in FM June 08. Unfortunately many doctors will accept this ‘research’ and tell patients not to bother with anti-mite measures.

The damp climate of the British Isles is ideal for mites, the commonest cause of rhinitis and asthma in children, but control is possible. A recent film on Channel 4 demonstrated a dramatic improvement in asthma after anti-mite measures were taken.
(For more information see www.allergiesexplained.com)

Other environmental allergies
Anything in the environment is suspect, even animal or fish foods (especially those containing mosquito larvae), which may be touched by hands. Identifying the cause often depends on the patient observing when symptoms occur and connecting it to contact with something in the house or at the workplace.

The working environment can also be involved, especially if it involves contact with animals, animal feed, chemicals, saw-dust and many other dusts. If symptoms become progressively worse from Monday to Friday, and are better at weekends or on holiday, an occupational allergy should be suspected. The reverse pattern (better at work in the week) points to an environmental allergen constantly present at home. A diary of symptoms or daily peak flow meter readings can be very helpful.

Food intolerance
Foods seldom cause anaphylaxis, and a food allergy may be obvious and lead to avoidance. Food intolerance is much more common as a cause of chronic illnesses affecting any part of the gut or any system of the body. Skin and blood tests are very helpful in allergy, but there are no reliable skin or blood tests for intolerance. As a result diagnosis usually depends on dietary manipulation and keeping a detailed diary of everything that passes the lips. Coeliac disease can cause many similar symptoms which remain undiagnosed for years, but should be excluded by a blood test available on NHS.

Few foods diet
The main difficulties in recognition of specific foods as a cause of chronic illness are that reactions are very often delayed to next day or longer, and several foods can be involved. The best way to exclude the possibility is to live on a diet including only the few foods which hardly ever cause problems for several weeks: rice, fish, game, lamb, and most fruit and vegetables (except potato and citrus fruit), beer and wine. If this restricted diet seems to make matters worse one of these foods could be the cause, but this is rare.

Some cases of irritable bowel syndrome and ulcerative colitis are food related, but this possibility is usually dismissed by sceptical specialists.
Constant bowel problems over many years are stressful, confusing cause with effect and creating a vicious circle.

Nobody knows how often food intolerance is the problem because dietary manipulation is seldom suggested so it may be worth trying, especially as there is little to lose except a few pounds in weight.
Improvement may be slow or disappointing, but in a longstanding problem semi-permanent changes may have occurred. This diet should be persisted with for long enough to be reasonably sure that it is not helpful (four to six weeks) but never permanently. To prove that a food is responsible for a problem it is essential to establish that the few foods diet brings about definite improvement, and the sooner improvement occurs the more likely it is that intolerance the answer.
If there is no difference give it up and go back to an ordinary diet. If there has been definite improvement the next step is to introduce foods one by one to find out which food will trigger a return of the symptoms. Much self-discipline is required at this stage, careful notes made daily, and normal amounts of the foods introduced while symptoms are absent.

To be quite certain it is desirable that the same amount of food should be found to have the same effect after the same delay on three occasions. As long as common sense is used and excessive amounts of food are not re-introduced too quickly this sort of problem can often be sorted out satisfactorily.

Eczema can often be caused by foods, but this is more common in infancy that in adult life. Unfortunately food is seldom considered as a cause partly because, in this country, it is uncommon for skin specialists to consider food allergy or to carry out prick skin tests. Onset of eczema on weaning is an obvious clue pointing to a food recently introduced, such as egg. Very occasionally the diet of the mother is the cause of eczema in breast-fed infants, and the commonest foods to cause reactions are milk, egg, wheat, soya, fish and nuts.

Recent evidence suggests that using creams containing peanut oil on the skin sensitises the child so that the first time peanut is eaten a reaction may occur. In later life allergy to environmental allergens, especially the dust mite, can be very important causes contributing to persistent eczema, but a food intolerance or allergy may also be lurking unseen in the background and can only be excluded by a diet trial.

Also see Dr Morrow Brown's site at www.allergiesexplained.com

First published in 2008

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