• Question: @Franco Why do people get allergic reactions?

    Asked by ... to Franco on 20 Jun 2016.
    • Photo: Franco Falcone

      Franco Falcone answered on 20 Jun 2016:

      This is a complicated issue. On one hand, it is a matter of your genes. Your parents can predispose you to allergy meaning that your chances of becoming allergic are higher than others. Individuals with such a predisposition without allergies are called atopics. Then there are environmental factors, such as different types of pollution, or exposure to the sources of allergy. If you have never encountered a cretain tree pollen ( for example because these trees do not grow where you live) then you cannot become allergic to it. This initial phase is called sensitisation, that’s the phase where your immune system starts producing certain antibodies called IgE, but you initially have no symptoms.

      And also the route of exposure is important, you can become allergic to wheat used in sosmetics through your skin and mucosa, but not when you eat it. Generally, eating food induces what is called tolerance.

      Finally, some parasites can protect you against developing allergies, but sadly. most of us living in the UK do not have these parasites although they were quite widespread in the past. So a small amount of certain parasites can be good, but if you have too many, the bad side of infection will prevail!

      Also it is important to remember that you can become allergic at any age, some people can become allergic e.g. to house dust mites when they are 60 or older, while many food allergies (milk and egg) normally disappear when children grow up.

      The allergic reaction itself is caused by a substance called histamine which is released by two types of cells, called basophils and mast cells, that are in your blood and skin, respectively, but only if you are allergic and get in touch with the substances you are allergic to. Histamine increases the diameter of your blood vessels, makes your skin red and hot and your eyes feel itchy, will induce your nose to run and make you sneeze. These symptoms can be blocked by using so-called antihistamines, which you can buy in Pharmacies and even Supermarkets.

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