THE PATTERN OF ALLERGY
The pattern of disease varies widely. Some people develop allergies very early in life, develop new allergies readily and have wide-ranging problems for most of their lives. Other people can show no sign of trouble, and then develop one or more allergies much later in life, often for no apparent reason. The severity of reaction also varies greatly from individual to individual.
The first time an allergen is encountered, it sets off the primary response from the immune system, to manufacture antibodies to it. No reaction will occur at this first meeting; it is not until the next encounter, or often some time later if you have a particularly heavy exposure to something, that you will react.
Babies in the womb can become sensitised to substances, especially foods, passed from the mother, so they can appear to be born with allergies. Preconceptual and antenatal care can help avoid or minimise this and it is worth taking precautions if you have any history of allergy in the family, not just in the mother (> CHARITIES).
Sensitivity to allergens can vary a great deal. Some people find, for instance, that if they eliminate allergens from their own home or work environment, they can tolerate them reasonably well when they meet them elsewhere. Some people, who live abroad for a while and then return to the UK, find that their level of tolerance to native pollens can change. Other people find, however, that their sensitivity remains very high and lifelong after initial sensitisation, and they have to take extreme care to avoid allergens completely.
The immune system appears to be able to recognise molecules or substances that are related to each other. This means that you are more prone to develop an allergy to something chemically or biologically related to a substance you are already allergic to. In some people, this never happens, but in others, ‘cross-reaction’ or ‘cross-reactivity’ is quite a strong phenomenon. You may need to take care to prevent cross-reaction.
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