In this study non-IgE-reactive recombinant Bet v 1 (rBet v 1) fragments (F1: aa 1-74; F2: aa 75-160) and the fully IgE-reactive recombinant Bet v 1 (aa 1-160)will be used for skin prick testing and atopy patch testing in birch pollen allergic patients with birch pollen induced exacerbation of atopic