VITAMIN supplements have not, as was feared, been outlawed. The Government has, however, made their availability subject to stringent regulation. The Government suggests, just like an old-fashioned nanny telling Master Tommy to finish his greens, that instead of vitamin supplements we should not be so remiss about taking our five helpings of fruit and vegetables a day. Good advice, but it is a reasonable bet that many of the fruits they recommend are more likely to cause trouble to someone than the near-harmless vitamins, when these are taken in the correct amount.

Nearly all fruits have adverse effects, usually only to the digestive system, if eaten in excess. The effects of apples, greengages, plums, apricots and rhubarb were well known long before Bernard Shaw wrote The Doctor’s Dilemma in 1906. In Shaw’s play the doctor working in the poverty-stricken slums relied on the laxative effect of greengages to maintain the success of his medical practice.

Few people are aware that allergies to fruits are relatively common, although fortunately they are rarely serious or life-threatening. Allergy is quite different from food intolerance. When a person suffers from a true allergy they are hypersensitive to a particular protein in the food (which is known as the allergen). This hypersensitivity overstimulates the immune response and production of the IgE antibody — the antibody produced by genuine allergic response. Conversely, food intolerance is characterised by an abnormal reaction to the taste, smell or even sight of the food. The symptoms may be related to an abnormality of the digestive system or triggered by a reaction to some chemical in the food. This reaction, for example, may cause migraine or abdominal symptoms, but there is no change to the IgE immune response.

Few families walking or playing in birch woods when the pollen is about realise that the allergic response it induces (and the running eyes, sneezing, congested or dripping nose, even the wheeze) may, thereafter, extend to other pollens, fruits and nuts. Fifty per cent of patients who are hypersensitive to birch pollen are also sensitive to apple. Apple seeds, apple pulp and hazelnut all share the allergens that can excite the specific IgE antibody reaction in birch pollen. There is even an association between apple allergy and a reaction to potatoes and carrots.

Strawberries have been cultivated since Roman times, but the modern strawberry originated in France after hybridisation of two wild American strains. Recently, many new varieties have been introduced that allow the season to be prolonged. Fortunately, some of these have a better taste than the earlier hybrids. Yet as strawberries become more common, so the number of reported cases of strawberry reaction rises.

Most of these cases are skin reactions, and young children are especially prone. The vulnerable child or, less commonly, adult may have itchy hands when they have handled the leaves or fruit, and once they have eaten it their lips and tongue may swell, their mouth itch and the throat become sore and uncomfortable.

John von Radowitz, the science correspondent of the Press Association, reported recently on the work done by Dr Rikard Alm, of Lund University in Sweden, on the site of the allergen in strawberries. For some years it has been suspected that either the colouring of the fruit or the aromatic compounds in it may contain the allergenic protein. Dr Alm’s work seems to confirm that it is probably the protein that gives the fruit its red colour. Experiments have shown that when vulnerable people handle or eat the white strawberry, which contains only a trace of the protein, they are almost free of adverse effects. Strawberry allergies are a nuisance and may deprive some children of one of the joys of family life in the country — picking and eating strawberries. But there may be problems, too, with one of the other fruits recommended as suitable in our daily fruit and veg ration: the kiwi.

Although most people can enjoy the kiwi’s nutritional benefits, a few are allergic to it. For some of those few, the allergy results not only in itchy fingers and sore lips but in anaphylaxis and spasm of the throat and mouth — a serious condition, particularly as, once people become allergic to kiwi, there is a risk of cross-reactivity with other seeds, nuts, fruit and pollens.