An ELISA-based CRD study conducted in Taiwan, enrolling Blattella-sensitized patients with persistent asthma and including recombinant Per a 1 through Per a 7 and Per a 9, revealed a reactivity with Per a 2 and Per a 9 to be associated with severe asthma and allergic rhinitis, respectively (12). Here, PER1 is linked to asthma.