What is an
allergy? It is a major defence mounted
by the body's immune system
against normally harmless substances, or allergens, such as chemicals in pollen, food,
bee stings, animal dander, or dust. An allergic reaction is the body's strong
reaction to these substances in a person who is sensitive to them. An allergy is everything from a runny
nose, itchy eyes and palate to skin rash. It aggravates the sense of smell,
sight, tastes and touch causing irritation, extreme disability and sometimes
fatality. It occurs when the body's immune system overreacts to normally
harmless substances.
Almost anything
can be an allergen for someone. Allergens contain protein, which is often
regarded as a constituent of the food we eat. In fact, it is an organic
compound, containing hydrogen, oxygen and nitrogen, which form an important
part of living organisms.
The most common
allergens are: pollen from trees and grasses, house dust mite, moulds, pets
such as cats and dogs, insects like wasps and bees, industrial and household
chemicals, medicines, and foods such as milk and eggs. Less common allergens
include nuts, fruit and latex.
There are some
non-protein allergens, which include drugs such as penicillin. For these to
cause an allergic response they need to be bound to a protein once they are in
the body.
An allergic
person's immune system believes allergens to be damaging and so produces a
special type of antibody (IgE) to attack the invading material. This leads
other blood cells to release further chemicals (including histamine) which
together cause the symptoms of an allergic reaction.
Appreciate when
asthma, eczema, headaches, lethargy, loss of concentration and sensitivity to
everyday foods such as cheese, fish and fruit are taken into account the full
scale of allergy.
Who are prone to
be a sufferer of allergy reactions? The answer is three-fold. First, your genetic background plays a major role - we know that a
family history of allergies or "Atopy" is highly significant, smaller
families with fewer children favour the development of allergy. Males are more
likely to develop allergies than females, and prenatal maternal diet and smoking
seem to play a role. Obesity also seems to be a risk factor for developing
allergies.
In the second place,
the home environment in the first year of life is pivotal. Parental cigarette
smoking triggers allergy, Infant diet, and early introduction of allergenic
foods play a role. Air Pollution has been implicated; early use of day-care
institutions, early use of broad-spectrum antibiotics and birth just before the
spring pollen season all seem to promote allergic sensitisation. Recent studies
suggest that heavy exposure to dog and cat allergens in the home may actually
prevent allergies developing in infants (they suggest having two or more pets
in the home!)
Finally, modest exposure to
the common aeroallergens and allergenic foods in conjunction with these other factors leads to sensitisation in early
life and clinical allergy then develops. Modest early exposure seems to
be the key to triggering sensitisation, as evidence now exists for very high
allergen exposure during early life having a "protective" effect (for
example to cats and dogs). However, minimal exposure during the first year of
life is still the recommended "rule of thumb" for allergy prevention.
