Being sensitised means that the immune system has come into contact with an allergen; committed it to its memory; synthesised IgE antibodies against it and is ready to launch a defence reaction when the allergen reappears. The time it takes to become sensitized to an allergen varies from person to person (from a few days to several years).
Very often allergy sufferers are said to be atopic. So what does this mean? Is it the same thing as allergy? The answer is not simply yes or no.
Atopy is the genetic predisposition of an individual to produce high quantities of IgE in response to allergens in the environment (pollens, house dust mites, moulds, cat dander, foods etc).
In addition to allergic diseases there are the so called pseudo-allergies. These maladies have similar symptoms with allergies (i.e. skin rash, itching, sneezing, runny nose, coughing, wheezing etc.).