Herbal Health

Histamine is one of the mediators released by mast cells when they degranulate. It is also released by various other cells in the body, since it acts as a local messenger substance, conveying instructions to neighbouring cells.

The main effects of histamine are to make smooth muscles (in the bronchi, gut, bladder etc) contract, to make the small blood vessels enlarge, and to make the capillaries (tiny blood vessels) become more leaky. These last two effects cause a drop in blood pressure. Locally, the increased leakiness of the capillaries contributes to inflammation.

Antihistamines (more correctly referred to as ‘histamine H1-receptor antagonists’) block the effects of histamine. They do this by binding to the H1 receptors on cells. Histamine normally binds to these receptors triggering off a reaction by the cell. So by blocking the receptors, antihistamines prevent histamine from affecting those cells.

There are a wide range of antihistamines available today. Most of these are rather unspecific and can also bind to the receptors for other messenger substances, such as adrenaline and serotonin. They tend to cause drowsiness through blocking messengers such as adrenaline, and they can also cause dizziness, nervousness, tremors, stomach upsets, dry mouth, blurred vision and impotence. These side-effects are not damaging in the long term, although they can be inconvenient. Some patients develop a tolerance of these drugs after a while, and the side-effects diminish. So if an antihistamine controls the allergic symptoms well, but causes side-effects, it is worth persisting with it for a while. Sometimes the sedative effects of antihistamines can be advantageous, as in children with urticaria who tend to scratch at night.

More specific drugs, which show a stronger preference for histamine receptors, have now been introduced. Astemizole (Hismanal) and terfenadine (Triludan) are the main ones. These can have some side-effects but should not cause as many problems as the other antihistamines.

Antihistamines, taken by mouth, are useful in hay-fever and perennial rhinitis, where there are symptoms in both the nose and eyes, together with itching in the mouth or ears. Where there are only symptoms in the nose, a sodium cromoglycate or corticosteroid spray may be more appropriate, as these have fewer side-effects. Some medicines contain antihistamines combined with sympathomimetics (see Section 3).

Antihistamines are also effective in some cases of chronic urticaria.

including cold-induced urticaria. They are not effective in asthma, because other mediators, besides histamine, play a major role in producing the symptoms.

2A Antihistamines

acrivastine (Semprex) astemizole (Hismanal) brompheniramine (Dimotane) cetirizine (Zirtek)

chlorpheniramine (Piriton, Haymine) clemastine (Tavegil) dimethindene (Fenostil) diphenylpyraline (Histryl Spansule, Lergoban)

hydroxyzine (Atarax) mebhydrolin (Fabahistin) mequitazine (Primalan) oxatomide (Tinset) phenindamine (Thephorin) pheniramine (Daneral) promethazine (Phenergan) terfenadine (Triludan) trimeprazine (Vallergan) triprolidine (Actidil, Pro-Actidil)

Ketotifen (Zaditen) acts both as an antihistamine and a mast-cell stabilizer (Section 1), and is used to prevent asthma attacks. Its side-effects are similar to those of most antihistamines.

Azatadine (Optimine) and cyproheptadine (Periactin) act both as antihistamines and serotonin antagonists. They are used for allergic rhinitis and urticaria.

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The reintroduction phase should take about seven or eight weeks. If it takes any longer than this, there is a risk of lost sensitivity: the food-intolerant person becomes less reactive after avoiding the culprit food for a time. If you are still testing foods eight weeks after starting the exclusion phase, then you need to test the foods more rigorously still. This means eating each reintroduced food every day for a week before declaring it safe.

If there are some foods that you have still not tested after 12 weeks then you have two options. One is to reintroduce all those foods for three to four weeks and see if any symptoms return. If they do, cut all those foods out again, wait until you feel better, then reintroduce them one at a time. Use three-day testing for preference, or one-day testing if you have a lot to get through.

The second option is to reintroduce each of the foods in turn, one per day. If there is no reaction, continue eating the food, but only on a once-every-four-days basis, for about six months. After that time, you should have become much less sensitive and be able to eat all these foods more freely.

If you suspect that you are sensitive to pesticide residues, you should be eating mainly unsprayed food during the exclusion phase of the diet. When you come to test foods, you should test unsprayed versions first, then a sprayed version of the same food, to see the difference. Leave a gap of at least four days between tests – try some other food in the meantime.

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One of the step up from here is the few-food diet or the rare-food diet. On a few-food diet the exclusion phase consists of a dozen or more foods that most people do not eat all that often. The exact foods chosen vary from one doctor to another, but they tend to include things such as parsnips, turnips and carrots which most of us do not eat in great quantity. The allowed foods also vary from patient to patient, because the doctor will ask the patient if any of the foods on the allowed list are eaten often – if they are, these must be excluded too. Most doctors have a second version of their few-food diet, with a different list of allowed foods: patients who do not get better during the first exclusion phase are switched to the second diet, in the hope that they will fare better. Of course, there is always a chance that both lists will include one or two foods which cause symptoms.

The rare-food diet is an extension of the few-foods idea, but instead of the patient eating uncommon foods such as turnips or parsnips during the exclusion phase, they are asked to eat exotic items such as yams or buckwheat. Since these items may never (or only rarely) have been eaten before, they are very unlikely to cause any reaction. In a sense the rare-food diet is an improvement on the few-food diet, because if the person fails to get better during the exclusion phase, they are probably not food-sensitive. With the few-food diet there is always some doubt – perhaps they were sensitive to parsnips, even though they only ever ate them for Sunday lunch? The drawbacks of the rare-food diet are principally cost – exotic foods are expensive -and the problem of getting such foods for those who do not live in a large city. The foods have to be prepared differently and the taste may take some getting used to, but on the whole they are at least as palatable as turnips! For those with multiple sensitivities who can afford the exotic foods, and have access to them, this type of diet is well worth considering.

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Do not attempt any diet without consulting your family doctor or specialist. If your child is under a child psychiatrist who is totally unsympathetic to dietary ideas, then ask your family doctor to refer you to someone else – an allergist for example, or a more open-minded psychiatrist – who will be prepared to supervise an elimination diet.

The specialist may have their own preferences as regards the diet, but if not. Children may need a calcium supplement, to compensate for the lack of milk in the diet, and the doctor can prescribe this. Children who also have asthma should be tested cautiously. Any child who has had severe allergic reactions in the past should not be tested for foods at home as the reaction can occasionally be life-threatening.

Drugs used to control behaviour, such as amphetamine derivatives, can be continued during the diet. If there appears to be an improvement in behaviour then you can try delaying the medication, or reducing the amount, but keep an eye on the situation and be prepared to top up the dose if necessary. Drugs used to control specific symptoms such as asthma or hay-fever should not be used routinely during the diet – only use them if they are actually needed. Needless to say, you should discuss all these points with your doctor before making any changes to the child’s medication.

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Antibodies are Y-shaped molecules, as the picture opposite shows. At the tip of each arm is an antigen-binding site where the antibody can bind to the particular feature of the antigen that it recognizes. These antigen-binding sites are the most changeable part of the antibody molecule – they vary enormously from one antibody to another. Their chemical structure determines which antigen is bound by that antibody.

The stem of an antibody can also vary, although nothing like as much. There are five basic types of stem, and they produce five different types of antibody, known as isotypes. The names of these isotypes (in order of abundance) are: IgG, IgA, IgM, IgD and IgE. In all cases the letters ‘Ig’ stand for immunoglobulin – another name for antibody. Imbalances between the different isotypes of antibody may play a role in food intolerance,

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