Medsarticles. Medical Weblog

These drugs have the effect of stabilizing mast cells so that they do not release histamine and other mediators. The main one used is sodium cromoglycate. It is only effective if it reaches the mast cell before the allergen. So it can be used to prevent the symptoms of allergy, as long as the patient remembers to take the drug when they are feeling well, before they encounter the allergen.

The drug is given in inhalers (Intal) as a preventive treatment for asthma. The time from when treatment starts to when the good effects become noticeable is variable – from a few days to several weeks. The drug must be taken continuously to be effective. In some people, it can cause irritation of the throat, coughing or, more rarely, an asthmatic attack. In rare cases there may be a true allergic reaction to the drug. In general, however, sodium cromoglycate is remarkably free of side-effects.

Although the main effect of sodium cromoglycate is to stabilize mast cells, it appears to make the bronchi less reactive in other ways as well. Thus it is used for exercise-induced asthma. Its long-term effect is to make the bronchi less sensitive, which is beneficial.

A related drug, nedocromil sodium (Tilade), is sometimes prescribed instead of sodium cromoglycate for asthma. It acts in much the same way but is a more powerful drug, and is not prescribed for children. Sometimes sodium cromoglycate is combined with other drugs, as in Intal Compound which contains isoprenaline.

In cases of food allergy, taking sodium cromoglycate by mouth (Nalcrom) can block the allergic reaction. But it is only used where the symptoms are not of the immediate-and-violent kind. Thus it might be prescribed for patients with food-induced symptoms such as diarrhoea, asthma, rhinitis, eczema or chronic urticaria, but not for those who suffer swelling of the mouth and tongue on eating a particular food. In such cases, the slight risk of the drug not working has to be considered, because of the serious consequences of such a failure.

Sodium cromoglycate appears to block mast cell degranulation in the gut wall, which prevents the gut wall becoming inflamed and thus makes it less permeable to food molecules.

To be effective, sodium cromoglycate (taken by mouth) must be taken 10 or 15 minutes before the food is eaten. The beneficial effects of the drug may not appear for several days. Occasionally, the drug may make the symptoms worse, for reasons that are not yet understood, and sometimes it has no effect, or only

partially controls the symptoms. Sometimes patients experience side-effects such as headaches, urticaria, diarrhoea or vomiting.

Because of doubts about its effectiveness if used long-term, simply taking sodium cromoglycate is not the best way to deal with food allergy. Its main use is in patients with reactions to a very wide range of foods, who find it difficult to avoid them all. Even though they are taking the drug, such patients must usually restrict their intake of the main offending foods as well. Babies who react to a wide range of foods on weaning have been helped by sodium cromoglycate.

This drug can also be useful in giving food-allergic people a ‘day off from their restricted diet. Children may be given it for Christmas or birthdays, to allow them to eat normally for a day. Sodium cromoglycate is also used in hay-fever and other forms of allergic rhinitis (Rynacrom) and in allergic conjunctivitis (Opticrom). It can cause stinging when applied but this wears off quickly and again there are no serious side-effects. The drug must be used regularly and consistently for the good effects to be maintained. In Rynacrom Compound, sodium cromoglycate is combined with xylometazoline, a sympathomimetic .

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Wait until you have been free of symptoms for two or three days, but don’t wait any longer than this. Begin by testing foods that are probably not the cause of any trouble – things you do not eat very often. Choose items that you like – if the foods pass the test, then you can incorporate them into your menus, which will allow you to eat less of the exclusion-phase foods. Throughout the reintroduction phase it is vital that you keep your diet varied and do not eat too much of any one food. In particular, do not eat any one food every day. Continue to record everything you eat, and your symptoms – if something goes wrong, this record will prove invaluable.

Only test one food at a time. Eat a normal-sized portion of the food in question, preferably with your evening meal. Notice any changes that occur at the time, or later in the evening, or the following day. During the first five weeks of testing, test each food for one day only. (Although eating the food for three days in succession is preferable, it takes so much time that you cannot test enough foods – there are far more to test than on Stage 2). If you think you may have reacted slightly, but are unsure, then test the same food again the next day.

After five weeks, your sensitivity may be declining, so you need to test each food more thoroughly, by eating it for three days in succession. If you get no reaction by the fourth day, then the food can be considered safe, but avoid it again for four days (to offset any possible effect of eating it for three days in succession) before beginning to eat it once more.

If you get a reaction to any food, stop eating it immediately. Allow the symptoms to subside before testing any more foods.

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Although all elimination diets work on the same principle, doctors differ considerably in the sorts of food they allow during the exclusion phase. The objective is to avoid all foods that are likely to cause problems. In essence, this means all foods that are eaten frequently because these are the most likely culprits. However, the ’safeness’ of foods is also taken into consideration – some foods seem less likely to cause problems than others. The question is – how far do you take this? Some patients will be sensitive to 20 or more foods – to get better, they need to avoid almost everything they normally eat. But these patients are a tiny minority. Most patients will be sensitive to between two and five foods. For them, a rigorous exclusion phase is not necessary – they simply need to avoid the most frequent offenders, such as wheat, milk, eggs, citrus fruits, yeast, chocolate and additives. On the whole, the latter group have a much easier task ahead of them in discovering which foods make them ill, so doctors tend to think more about the unfortunate patients with multiple sensitivities. With them in mind, they devise diets that will eliminate most commonly eaten foods, even if this means putting the patients with just a few sensitivities through an unnecessarily arduous regime. The approach to elimination diet that we recommend is a flexible three-stage procedure that provides the best possible diet for each type of patient.

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The first step for any parent is to decide whether their child’s behaviour really is abnormal. As Dr Philip Graham of the Institute of Child Health in London points out: ‘All normal children show some degree of aggressiveness, disobedience and antisocial behaviour: all at times show sadness, depression, anxiety and social withdrawal. All are at times unusually active and distractible. What makes a child a cause for concern is the severity and persistence of the problematic behaviour in question.’

Although a child like Matthew clearly shows abnormal behaviour, others with hyperkinetic syndrome may only be mildly affected. In such cases, it may be quite difficult to distinguish hyperkinetic syndrome from ‘normal’ behaviour – emotional upset and misconduct may be due to family tensions, lack of discipline, an unsettled home life, difficulties at school, or a great variety of other causes. It is very tempting for parents to attribute their child’s awful behaviour to some simple external cause when the real problem lies within the family. Conversely, some parents may find lively, childish behaviour disruptive and label it as ‘hyperactive’ when in fact it is perfectly normal. Parents may not always be the best judge of what is wrong with their child, and it is a good idea to discuss the problem with a sympathetic teacher, doctor or child psychiatrist, keeping an open mind about the possible causes of the problem.

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Antibodies are special molecules produced by the body to fight off infections. They bind firmly to the bacteria or virus that causes the infection and, with luck, this stops the infection in its tracks. Antibodies can block infection in a variety of ways. With viruses, they may be able to prevent them from invading the body’s cells simply by binding to them. With bacteria, however, antibodies alone are ineffectual. They need help to defeat the bacteria and their job is to act as signals to other cells and molecules in the body which have the power to kill. The antibodies form a coat on the surface of the bacterial cells and this stimulates the immune system’s ‘assassination teams’ to go into action against the bacteria.

Antibodies are protein molecules, as are many of the important, hardworking components of the body (see p23). Proteins are infinitely variable molecules and this is what makes them so useful. In the case of the antibodies, their versatility is employed in making molecules that bind specifically to a particular target molecule, or antigen, and to no other. The measles virus, for example, is bound by antibodies that specifically recognize proteins in the outer coat of the virus – these being the measles antigens. They do not normally bind to anything else, apart from the measles virus.

The body produces a vast range of different antibodies – millions of them so that if it has to combat a new bacteria or virus it is certain to find an antibody ‘in stock’ that is just right for it. The antibodies are produced by special factory cells called B cells, and each B cell produces its own particular form of antibody. When faced with an invading microbe, the body selects a B cell with the right antibody to match that microbe, stimulates the cell to divide, and then instructs all the cells that are descended from it to produce their much-needed antibody. This continues until there is enough of the correct antibody to defeat the infection.

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