Is allergy an inborn condition?i never had an unpleasant skin allergy(very itchy skin rashes) before until i turned 21.

Yes and no: While you may be born with a propensity toward developing allergies genetically, you actually have to be exposed to an allergen before you become allergic to it. It could happen the first time you are exposed or the hundredth. I, like you, did not start having hayfever symptoms until I was in my 20's. Yet every fall when ragweed is out, symptoms start unless I take my meds during that time of year