Miss L.P., a 28-year-old single woman, was troubled by cold sores, which seemed to be triggered by citrus. She was an avid drinker of normal English tea with milk, but had recently got into the habit of having a grapefruit each morning. She was convinced that the grapefruit was causing the cold sores.

I agreed that this was quite possible because such an allergic response could weaken her immune system’s ability to control outbreaks of the resident herpesvirus that brought on the cold sores, and advised her to stop having any grapefruit or other citrus. But she wouldn't hear of it and left, feeling a little disgruntled.

Three months later, she came in again to tell me that she had cured herself of the cold sores, although she was still having grapefruit every morning. She had also moved in with a man who was a serious coffee drinker: the beans had to be freshly ground, then brewed in an espresso maker. That didn’t leave much time for her own teapot ritual, so she had become a coffee-drinker, too.

I told her that she was probably more sensitive to the coffee than to the citrus, so that her immune system was ignoring the grapefruit. I also felt she was reacting to the coffee in some way.

I pointed out two facts to her: one, that hypersensitivity reactions could be temporarily displaced in the presence of a major allergen, which acts rather like a lightning-rod since there is a ‘pecking order’ in allergic reactions; and two, that there were so-called ‘masked allergies’, in which the reaction is not immediately apparent. For example, if the swelling in allergic asthma was not in the lungs, but somewhere in the body where it didn't interfere with breathing or any other function, it would not be noticed. Similarly, she could be sensitive to coffee, but simply unaware of it.

This is ‘cure by distraction’, I told her, where the immune system reacts to what is higher up in the pecking order of physical ‘threats’, so that it ignores the less important ones, at least for the moment. In addition, the reaction could well be in the form of a ‘masked allergy’. At this, she let out a derisory laugh and replied, “I am simply not sensitive to coffee!”

Five months later, Miss L.P. visited me again, this time to tell me that, two months earlier, she had begun to notice that the morning coffee was causing pain in the liver region, and that she now was back to drinking tea and had stopped all citrus. The result was no pain - and no cold sores.

This case illustrates how complicated it can be to determine an allergy unless you take into account everything you're exposed to, and eliminate each one, in turn, as your own medical detective.

Harald Gaier

Harald Gaier is a registered naturopath, osteopath, homoeopath and herbalist. He can be contacted at The Diagnostic Clinic, London, tel: 020 7009 4650