Hi.. Thanks for the query.. I think you are allergic to something that you are being exposed continuously.. Due to this only as soon as the effect of the anti allergics ceases the symptoms flare up.. See, the anti allergics just reduce the allergy symptoms and do not treat them. So the best way is to avoid exposure to allergen. So it is important to consult an Allergist and get an Allergic test done like RAST test, patch test, food challenge test etc. Once you know the allergen, avoid exposure to it.. Fir now continue taking anti allergics.. You can also talk about Immunotherapy to your Physician once the allergen is ruled out.. Hope this helps .