UNEXPECTION ALLERGIC CROSS-REACTION: CROSS-REACTIONS BETWEEN PLANT PRODUCTS
Many of those who are allergic to birch pollen cannot eat hazelnuts. This is not particularly surprising, since birch and hazel belong to the same plant family. What is unexpected is the cross-reaction seen between birch pollen and apple – a very high proportion of those with birch hay-fever are allergic to apples. It is thought that this is due to small molecules called phenols that are widely distributed in plant products. The suggestion is that apple and birch just happen to have the same sort of phenol, despite their unrelatedness. There are other odd cross-reactions between different fruits and vegetables which may be explained in the same way.
Shellfish
Some people seem to be sensitive to both crustacean shellfish and molluscan shellfish. Why this should be is a mystery – it is unlikely to be a cross-reaction, in the conventional sense, since the two groups are not at all closely related. Biologically speaking, they are as similar to humans or birds as they are to each other. Again, the use of an imprecise name for both groups -’shellfish’ – is a confusing factor.
For certain people, it may be something other than the shellfish themselves causing the problem. Toxins acquired from their food, or the preservatives that are liberally added to shellfish might be to blame.
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