Reviewed by Dr Jeni Worden, GP
What is an allergy?
Allergy or hypersensitivity (type 1 allergy) is an abnormal reaction to protein substances that occur naturally.
If an allergic person is exposed to these substances called allergens, the body's immune system gets ready to fight them.
White blood cells (B-lymphocytes) produce an antidote (antibody) against the allergen. The antibody sticks to the surface of the allergy cells. Now the body is ready to fight back the next time it is exposed to the allergen. This process is called sensitisation.
After this change, there is an allergic reaction every time the body is exposed to the allergen.
The allergen sticks to the antibodies on the surface of the allergy cells. This coupling causes the granula (little stores in the allergy cells) to release histamine, which causes the symptoms of allergy.
Depending on the size of the exposure to the allergen and where on the body it happens, there will be an allergic reaction in the form of hay fever, asthma or nettle rash.
The histamine dilates the blood vessels, causes the mucous membranes (lining tissues of the nose and airways) to swell due to the liquid leaking and stimulates the glands in the nose and the respiratory passages to produce mucus (phlegm).
Substances that make the musculature of the respiratory passages contract are released along with the histamine. It becomes difficult to breathe and an asthma attack may follow.
An allergy is very different to an intolerance or sensitivity; there are on the whole no scientific replicable tests for food sensitivities, although it is now possible to test for gluten intolerance (as opposed to gluten allergy or celiac disease) with an NHS blood test available through GP's.
What are allergens?
Allergens are microscopic protein substances that are common and provoke allergic people to produce antidotes (antibodies).
The most common allergy provoking substances are:
Allergic people have very sensitive mucous membranes, which can be irritated by lots of different substances including smoke, pollution, cooking smells, perfume and strong odours.
Children who are often exposed to passive smoking are more at risk of developing allergic reactions.
Does hypersensitivity occur frequently?
The predisposition to hypersensitivity is hereditary.
If one or both parents or close family members suffer from hypersensitivity, it's advisable to talk to a doctor about how to lower the risk of the children developing it.
How can the doctor diagnose hypersensitivity?
It's often enough to tell the doctor when, where and how you get the symptoms. Then they can do an examination that involves skin tests and different blood tests. If asthma is suspected, breathing tests will be performed.
Treatment of allergy
|Based on a text by Dr Kirsten Hørder
|Last updated 30.11.2010
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