Dr Thomas Stuttaford answers your questions on food allergies and intolerance

Food intolerance is the condition in which a person may be unable to swallow - possibly only because of repugnance to the food’s taste or smell - or because of an abnormality in their enzyme production that may prevent its normal absorption, an inflammation of the gut. Although food intolerance may also give rise to generalised symptoms as there are no changes in the antibody levels these are not true allergies and there is no abnormal immune response. The physical cause, if any, of a case of food intolerance is often undetected.

From the description of your rash it sounds as if you might have a mild allergy to one of the constituents of chocolate. As you probably know the more expensive and the darker the chocolate, the more likely it is to have a high proportion of cocoa. In the cheaper brands, including the best known, the proportion of cocoa in the chocolate is very low. Although the expensive high-level of cocoa in your case may induce a rash, in most people it is better for them. The darker the chocolate, the richer it is in the anti-oxidants that have benefits for the cardiovascular system as well as other welcome effects on a person’s general health.

Q2: I became allergic to oysters about ten years ago, though I can and do eat other kinds of shellfish. I avoid eating a large amount of crab or lobster, for I get rashes if I do. Recently, rashes appear when I have had beef or sometimes pork. Does this mean that I am becoming allergic to other types of protein? Is there anything I could do, apart from not eating suspected sources? Thank you. Name and address withheld.

A2: Shellfish allergies are very common and it seems from your history that you have an allergy to shellfish. This is most obvious when you eat oysters. Once a patient has an allergy to one substance it is frequently found that the allergic tendency spreads to other substances. A few years ago the newspapers reported about the allergies suffered by a well known chef Shane Osborn. His allergy started after preparing scallops and lobsters but in time spread to other forms of fish and even mushrooms and aubergines.

Similarly once a patient becomes allergic to one type of tree pollen, berry or fruit doctors and the patient notice that he or she frequently becomes allergic to other berries and fruits. Likewise an initial allergy to one type of grass pollen, so that someone develops hay fever, rarely remains confined to that grass but spreads to a wide variety of grasses, flowers and trees.

I suspect that you are becoming allergic to other proteins as well as those in shellfish but another possible explanation is that your pork or beef has been cooked in saucepans or pans that have previously been used to cook shellfish. Only the smallest trace of the protein that is an allergen may be enough to stimulate a reaction. I would discuss your allergies with your doctor and ask if you can see an allergy specialist. The waiting list is usually a long one but if you know you have a tendency of developing an allergy it is as well to have it carefully defined. In some cases de-sensitisation is possible and techniques for this are improving year by year. No one can predict when an allergy might not suddenly become more serious. If this is considered a danger an Epi pen to give an immediate dose of adrenaline should be carried at all times. Meanwhile avoid shellfish.

Q3: I was diagnosed with a cashew nut allergy as a small child will I still be allergic? I’ve never tried the nut. Name and address withheld.

A3: Not necessarily but I wouldn’t risk it. Nut allergy is perhaps of all the allergies the one that seems to be the cause of the most severe and dangerous of symptoms. An allergy specialist can take a careful history and can perform skin and blood tests. If the allergy is likely to be serious the patient should not only avoid the precipitating foods and the utensils used to prepare them but should steer clear of all nuts. It might also be necessary for you to carry an Epi pen. These are very simple devices that enable you, or a friend to give an immediate injection of adrenaline if serious symptoms develop.

I have a godson who when he was small used to swell up alarmingly if he so much as touched an eggshell. I was surprised when I saw him recently that he, now aged 22, was enjoying a meal of bacon and eggs. He told me that as he grew older he slowly outgrew his allergy to eggs. Although this case had a happy ending it won’t have been achieved without taking, in my opinion, an unacceptable risk.

Q4: I have found that the comparatively-recently intoduced “lite” soft spreads which I used in place of butter, cause a rash on my arms and legs. When I take anti-histamine tablets the rash goes. Have you any idea what causes this and is it a common reaction, or am I the only one? Name and address withheld

A4: Almost certainly you have an allergy or sensitivity to one of the chemicals in the new lite soft spreads. I would recommend that you stick to butter. Although intolerance to dairy products is common, butter is relatively clear of additives so that you and your doctor know what you are dealing with.

Q5: What are the most common sources of allergens and allergic responses? Name witheld, Surrey.

A5: The most common allergen is probably the house dust mite. Every house, however spotless, has its resident population of house mites. These minute organisms are invisible to the naked eye but when looked at down a microscope are frightening. They live on flakes of human or animal skin that have been shed and become trapped by carpets, cracks in the floor, holes around the pipes and in bed linen. Other common allergens are found in pollens and these may cause allergic rhinitis (hay fever). Flakes of animal skin or hair from the household dog, cat or cage bird may also be responsible for allergies. The saliva left on an animal’s coat after they have been licking it is notorious for setting up an allergic response in the animal’s owner. Food allergies we have already discussed. The most common are eggs, cows milk and other dairy produce, nuts and shellfish. As with any allergy the first attack may be so mild that it passes unnoticed but years later someone may be re-exposed to the same substance and suffer a serious reaction.

Q6: I live near birch woods and have noticed that when there is pollen about I have all the signs of hay fever, runny eyes, sneezing, a congested and dripping nose and a wheeze. What should I do? Name and address withheld.

A6: There are many long acting antihistamines that can be taken by mouth and are not sleep inducing, so that you can still drive. Excellent steroid nasal sprays are available to relieve symptoms. Consult your doctor as he may recommend de-sensitisation and a visit to the allergy clinic. De-sensitisation now has to be supervised by a hospital so that if after any injection you are over sensitive to it the necessary first aid treatment is immediately available.

A word of warning about birch sensitivity. As time goes by this allergy may often also encompass apples, fruits including strawberries. There is even an association between apple allergy and a reaction to potatoes and carrots, but this is rather less likely whereas 50 per cent of people who are sensitive to birch pollen are also sensitive to apples.